Ink composition, inkjet recording method, printed material, process for producing lithographic printing plate, and lithographic printing plate

ABSTRACT

An ink composition is provided that includes (a) a polymerizable compound, (b) a polymerization initiator, (c) a coloring agent, and (d) a fragrance. There is also provided an inkjet recording method that includes a step of discharging the ink composition onto a recording medium, and a step of irradiating the discharged ink composition with radiation so as to cure the ink composition.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is based on, and claims priority from, J.P.Application 2005-137964, filed May 11, 2005, the disclosure of which ishereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink composition suitably used forinkjet recording, an inkjet recording method, and a printed materialemploying same; furthermore, it relates to a lithographic printing plateobtained using the ink composition, and a process for producing alithographic printing plate. More particularly, it relates to an inkcomposition suitable for inkjet recording that cures with highsensitivity upon exposure to radiation, can form a high quality image,and has little unpleasant odor originating from an ink component(hereinafter, abbreviated to odor), that is, a so-called low odor inkcomposition, an inkjet recording method, a printed material employingsame, a lithographic printing plate obtained using the ink composition,and a process for producing a lithographic printing plate.

2. Description of the Related Art

With regard to an image recording method for forming an image on arecording medium such as paper based on an image data signal, there arean electrophotographic system, sublimation type and melt type thermaltransfer systems, an inkjet system, etc. In the electrophotographicsystem, a process of forming an electrostatic latent image on aphotosensitive drum by electrically charging and exposing is required,and the system is complicated; as a result, there is the problem thatthe production cost is high. With regard to the thermal transfer system,although the equipment is inexpensive, due to the use of an ink ribbonthere is the problem that the running cost is high and waste material isgenerated. On the other hand, with regard to the inkjet system, theequipment is inexpensive and, since an image is formed directly on arecording medium by discharging an ink only on a required image area,the ink can be used efficiently and the running cost is low.Furthermore, there is little noise and it is excellent as an imagerecording system.

An ink composition that can be cured by exposure to radiation such asultraviolet rays and, in particular, an inkjet recording ink (radiationcuring type inkjet recording ink) are required to have sufficiently highsensitivity and provide a high image quality. By achieving highersensitivity, a large number of benefits are provided, such as highcurability toward radiation, a reduction in power consumption, longerlifetime due to a decrease in the load on a radiation generator, andprevention of formation of low molecular weight material originatingfrom insufficient curing. Furthermore, higher sensitivity particularlyimproves the cure strength of an image formed using the ink compositionand, in particular, the inkjet recording ink, particularly for theformation of a lithographic printing plate, and high plate life can beobtained.

Such a UV-curing inkjet system, which can be applied to recording on arecording medium that does not have quick drying properties or inkabsorbing properties, has recently been attracting attention, andUV-curing inkjet inks have been disclosed (ref. e.g. JP-B-5-54667,JP-A-6-200204, Published Japanese translation No. 2000-504778 of a PCTapplication; JP-A denotes a Japanese unexamined patent applicationpublication, and JP-B denotes a Japanese examined patent applicationpublication).

With regard to the UV-curing ink, there is a type comprising a radicallypolymerizable monomer, and a type comprising a cationicallypolymerizable monomer. For many of the type comprising a radicallypolymerizable monomer, the monomers used have an odor, and the odor is aproblem. On the other hand, the cationically polymerizable monomers havea relatively low odor, but there are some that have an odor.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention, which has been accomplishedunder the above-mentioned circumstances, to provide an ink compositionthat cures with high sensitivity by exposure to actinic radiation, canform a high quality image, has excellent adhesion to a recording medium,and has low odor, and an inkjet recording method employing the inkcomposition.

It is another object of the present invention to provide a printedmaterial and a lithographic printing plate obtained using an inkcomposition that has low odor and can be cured with high sensitivity byexposure to ultraviolet rays, and a process for producing a lithographicprinting plate.

The above-mentioned objects can be accomplished by (1), (10), and (12)to (14). (2) to (9) and (11), which are preferred embodiments, are alsoshown below.

(1) An ink composition comprising a) a polymerizable compound, b) apolymerization initiator, c) a coloring agent, and d) a fragrance,

(2) the ink composition according to (1), wherein the fragrance d)comprises a natural fragrance,

(3) the ink composition according to (1) or (2), wherein the fragranced) comprises a synthetic fragrance,

(4) the ink composition according to any one of (1) to (3), wherein thefragrance d) comprises an ester compound,

(5) the ink composition according to any one of (1) to (4), wherein thefragrance d) comprises a terpene compound,

(6) the ink composition according to any one of (1) to (5), wherein thepolymerizable compound a) is cationically polymerizable, and thepolymerization initiator b) is a photo-acid generator,

(7) the ink composition according to any one of (1) to (6), wherein thecoloring agent c) is a pigment or an oil-soluble dye,

(8) the ink composition according to (7), wherein the oil-soluble dyehas an oxidation potential of at least 1.0 V (vs SCE),

(9) the ink composition according to any one of (1) to (8), wherein itis for inkjet recording,

(10) an inkjet recording method comprising (a) a step of discharging anink composition onto a recording medium and (b) a step of curing the inkcomposition by irradiating the discharged ink composition with actinicradiation, the ink composition being the ink composition according toany one of (1) to (9),

(11) the inkjet recording method according to (10), wherein the actinicradiation is UV radiation having a peak light emission wavelength in therange of 350 to 420 nm and is emitted by a light-emitting diode foremitting UV radiation whose maximum illumination intensity on thesurface of a recording medium is 10 to 2,000 mW/cm²,

(12) a printed material recorded by the inkjet recording methodaccording to (10) or (11),

(13) a process for producing a lithographic printing plate, the processcomprising (a) a step of discharging the ink composition according toany one of (1) to (9) onto a hydrophilic support and (b) a step ofcuring the ink composition by irradiating the discharged ink compositionwith actinic radiation so as to form a hydrophobic image on thehydrophilic support by curing the ink composition,

(14) a lithographic printing plate produced by the lithographic printingplate production process according to (13).

DETAILED DESCRIPTION OF THE INVENTION

The ink composition of the present invention (hereinafter, also simplycalled ‘ink’) comprises (a) a polymerizable compound, (b) apolymerization initiator, (c) a coloring agent, and (d) a fragrance. Thepresent invention is explained in detail below.

(1) Essential Components of the Present Invention

(a) Polymerizable Compound

The ink composition of the present invention comprises (a) apolymerizable compound. Examples of the polymerizable compound that canbe used in the present invention include a cationically polymerizablecompound and a radically polymerizable compound, and the cationicallypolymerizable compound and the radically polymerizable compound may beused in combination. As the cationically polymerizable compound, forexample, a cationically polymerizable type photocuring resin is known,and in recent years cationically photopolymerizable type photocuringresins sensitized to a visible light wavelength region of 400 nm orlonger have been disclosed in, for example, JP-A-6-43633 andJP-A-8-324137. As the radically polymerizable compound, photocuringmaterials employing photopolymerizable compositions described in, forexample, JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, and JP-A-10-863 areknown.

(a-1) Cationically Polymerizable Compound (a)

The cationically polymerizable compound used in the present invention isnot particularly limited as long as it is a compound that undergoes apolymerization reaction by virtue of an acid generated by the photo-acidgenerator, which will be described later, and is cured, and varioustypes of cationically polymerizable monomers known as photo-cationicallypolymerizable monomers may be used. Examples of the cationicallypolymerizable monomer include epoxy compounds, vinyl ether compounds,oxetane compounds described in JP-A-6-9714, JP-A-2001-31892,JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937,JP-A-2001-220526, etc.

Examples of the epoxy compounds include aromatic epoxides, alicyclicepoxides, and aliphatic epoxides, and examples of the aromatic epoxideinclude di- or polyglycidyl ethers produced by a reaction betweenepichlorohydrin and a polyhydric phenol having at least one aromaticnucleus or an alkylene oxide adduct thereof; specific examples includedi- or polyglycidyl ethers of bisphenol A or an alkylene oxide adductthereof, di- or polyglycidyl ethers of hydrogenated bisphenol A or analkylene oxide adduct thereof, and novolac type epoxy resins. Examplesof the alkylene oxide above include ethylene oxide and propylene oxide.

Examples of the alicyclic epoxides include cyclohexene oxide- andcyclopentene oxide-containing compounds obtained by epoxidizing acompound having at least one cycloalkene ring such as a cyclohexene ringor a cyclopentene ring with an appropriate oxidizing agent such ashydrogen peroxide or a peracid.

Examples of the aliphatic epoxides include di- or polyglycidyl ethers ofan aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, andrepresentative examples thereof include diglycidyl ethers of an alkyleneglycol such as the diglycidyl ether of ethylene glycol, the diglycidylether of propylene glycol, and the diglycidyl ether of 1,6-hexanediol,polyglycidyl ethers of a polyhydric alcohol such as the di- ortriglycidyl ether of glycerol or an alkylene oxide adduct thereof, anddiglycidyl ethers of a polyalkylene glycol such as the diglycidyl etherof polyethylene glycol or an alkylene oxide adduct thereof and thediglycidyl ether of polypropylene glycol or an alkylene oxide adductthereof. Examples of the alkylene oxide above include ethylene oxide andpropylene oxide.

Detailed examples of monofunctional and polyfunctional epoxy compoundsthat can be used in the present invention are now given.

Examples of monofunctional epoxy compounds used in the present inventioninclude phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butylglycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether,1,2-butylene oxide, 1,3-butadiene monooxide, 1,2-epoxydodecane,epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide,3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexeneoxide, and 3-vinylcyclohexene oxide.

Furthermore, examples of polyfunctional epoxy compounds includebisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol Sdiglycidyl ether, brominated bisphenol A diglycidyl ether, brominatedbisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether,epoxy novolac resins, hydrogenated bisphenol A diglycidyl ether,hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol Sdiglycidyl ether,3,4-epoxycyclohexenylmethyl-3′,4′-epoxycyclohexenecarboxylate,2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane,bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene dioxide,4-vinylepoxycyclohexane, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexenyl3′,4′-epoxy-6′-methylcyclohexenecarboxylate,methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, thedi(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate), dioctyl epoxyhexahydrophthalate,di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidylether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether,trimethylolpropane triglycidyl ether, polyethylene glycol diglycidylether, polypropylene glycol diglycidyl ether, 1,13-tetradecadienedioxide, limonene dioxide, 1,2,7,8-diepoxyoctane, and1,2,5,6-diepoxycyclooctane.

Among these epoxy compounds, the aromatic epoxides and the alicyclicepoxides are preferable from the viewpoint of excellent curing speed,and the alicyclic epoxides are particularly preferable.

Examples of the vinyl ether compounds include di- or tri-vinyl ethercompounds such as ethylene glycol divinyl ether, diethylene glycoldivinyl ether, triethylene glycol divinyl ether, propylene glycoldivinyl ether, dipropylene glycol divinyl ether, butanediol divinylether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether,and trimethylolpropane trivinyl ether, and monovinyl ether compoundssuch as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether,octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether,2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether,n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl vinylether-O-propylene carbonate, dodecyl vinyl ether, and diethylene glycolmonovinyl ether.

Detailed examples of monofunctional vinyl ethers and polyfunctionalvinyl ethers are given below.

Specific examples of monofunctional vinyl ethers include methyl vinylether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether,t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether,lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinylether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether,dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether,methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinylether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether,methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether,2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutylvinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethyleneglycol monovinyl ether, polyethylene glycol vinyl ether, chloroethylvinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether,phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether.

Furthermore, examples of polyfunctional vinyl ethers include divinylethers such as ethylene glycol divinyl ether, diethylene glycol divinylether, polyethylene glycol divinyl ether, propylene glycol divinylether, butylene glycol divinyl ether, hexanediol divinyl ether,bisphenol A alkylene oxide divinyl ether, and bisphenol F alkylene oxidedivinyl ether; and polyfunctional vinyl ethers such as trimethylolethanetrivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropanetetravinyl ether, glycerol trivinyl ether, pentaerythritol tetravinylether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinylether, an ethylene oxide adduct of trimethylolpropane trivinyl ether, apropylene oxide adduct of trimethylolpropane trivinyl ether, ah ethyleneoxide adduct of ditrimethylolpropane tetravinyl ether, a propylene oxideadduct of ditrimethylolpropane tetravinyl ether, an ethylene oxideadduct of pentaerythritol tetravinyl ether, a propylene oxide adduct ofpentaerythritol tetravinyl ether, an ethylene oxide adduct ofdipentaerythritol hexavinyl ether, and a propylene oxide adduct ofdipentaerythritol hexavinyl ether.

As the vinyl ether compound, the di- or tri-vinyl ether compounds arepreferable from the viewpoint of curability, adhesion to a recordingmedium, surface hardness of the image formed, etc., and the divinylether compounds are particularly preferable.

The oxetane compound in the present invention means a compound having atleast one oxetane ring, and may be selected freely from known oxetanecompounds such as those described in JP-A-2001-220526, JP-A-2001-310937,and JP-A-2003-341217.

As the compound having an oxetane ring that can be used in the inkcomposition of the present invention, a compound having 1 to 4 oxetanerings in the structure is preferable. In accordance with use of such acompound, it becomes easy to maintain the viscosity of the inkcomposition in a range that gives good handling properties and,furthermore, the cured ink can be given high adhesion to the recordingmedium, which is preferable.

Examples of compounds having 1 to 2 oxetane rings in the moleculeinclude compounds represented by Formulae (1) to (3) below.

R^(a1) denotes a hydrogen atom, an alkyl group having 1 to 6 carbons, afluoroalkyl group having 1 to 6 carbons, an allyl group, an aryl group,a furyl group, or a thienyl group. When there are two R^(a1) in themolecule, they may be identical to or different from each other.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, and a butyl group, and preferred examples of thefluoroalkyl group include those obtained by substituting any of thehydrogen atoms of the above alkyl groups with a fluorine atom.

R^(a2) denotes a hydrogen atom, an alkyl group having 1 to 6 carbons, analkenyl group having 2 to 6 carbons, a group having an aromatic ring, analkylcarbonyl group having 2 to 6 carbons, an alkoxycarbonyl grouphaving 2 to 6 carbons, or an N-alkylcarbamoyl group having 2 to 6carbons. Examples of the alkyl group include a methyl group, an ethylgroup, a propyl group, and a butyl group, examples of the alkenyl groupinclude a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenylgroup, a 2-methyl-2-propenyl group, a 1-butenyl group, a 2-butenylgroup, and a 3-butenyl group, and examples of the group having anaromatic ring include a phenyl group, a benzyl group, a fluorobenzylgroup, a methoxybenzyl group, and a phenoxyethyl group. Examples of thealkylcarbonyl group include an ethylcarbonyl group, a propylcarbonylgroup, and a butylcarbonyl group, examples of the alkoxycarbonyl groupinclude an ethoxycarbonyl group, a propoxycarbonyl group, and abutoxycarbonyl group, and examples of the N-alkylcarbamoyl group includean ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoylgroup, and a pentylcarbamoyl group. Furthermore, it is possible for R²to have a subsituent, and the examples of the substituent include alkylgroup, having 1 to 6 carbons and fluorine atom

R^(a3) denotes a linear or branched alkylene group, a linear or branchedpoly(alkyleneoxy) group, a linear or branched unsaturated hydrocarbongroup, a carbonyl group, a carbonyl group-containing alkylene group, acarboxyl group-containing alkylene group, a carbamoyl group-containingalkylene group, or a group shown below. Examples of the alkylene groupinclude an ethylene group, a propylene group, and a butylene group, andexamples of the poly(alkyleneoxy) group include a poly(ethyleneoxy)group and a poly(propyleneoxy) group. Examples of the unsaturatedhydrocarbon group include a propenylene group, a methylpropenylenegroup, and a butenylene group.

When R^(a3) is the above-mentioned polyvalent group, R^(a4) denotes ahydrogen atom, an alkyl group having 1 to 4 carbons, an alkoxy grouphaving 1 to 4 carbons, a halogen atom, a nitro group, a cyano group, amercapto group, a lower alkylcarboxyl group, a carboxyl group, or acarbamoyl group.

R^(a5) denotes an oxygen atom, a sulfur atom, a methylene group, NH, SO,SO₂, C(CF₃)₂, or, C(CH₃)₂.

R^(a6) denotes an alkyl group having 1 to 4 carbons or an aryl group,and n is an integer of 0 to 2,000. R^(a7) denotes an alkyl group having1 to 4 carbons, an aryl group, or a monovalent group having thestructure below. In the formula, R^(a8) denotes an alkyl group having 1to 4 carbons or an aryl group, and m is an integer of 0 to 100.

Examples of the compound represented by Formula (1) include3-ethyl-3-hydroxymethyloxetane (OXT-101: manufactured by Toagosei Co.,Ltd.), 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane (OXT-212: manufacturedby Toagosei Co., Ltd.), and 3-ethyl-3-phenoxymethyloxetane (OXT-211:manufactured by Toagosei Co., Ltd.). Examples of the compoundrepresented by Formula (2) include1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (OXT-121: ToagoseiCo., Ltd.). Examples of the compound represented by Formula (3) includebis(3-ethyl-3-oxetanylmethyl)ether (OXT-221: Toagosei Co., Ltd.).

Examples of the compound having 3, to 4 oxetane rings in the moleculeinclude compounds represented by Formula (4) below.

In Formula (4), R^(a1) denotes the same as in Formula (1) above.Furthermore, examples of R^(a9), which is a polyvalent linking group,include a branched alkylene group having 1 to 12 carbons such as a grouprepresented by A to C below, a branched poly(alkyleneoxy) group such asa group represented by D below, and a branched polysiloxane group suchas a group represented by E below. j is 3 or 4.

In the above A, R^(a10) denotes a methyl group, an ethyl group, or apropyl group. Furthermore, in the above D, p is an integer of 1 to 10.

Moreover, as another embodiment of the oxetane compound that can besuitably used in the present invention, a compound having an oxetanering on a side chain, represented by Formula (5) below, can be cited.

In Formula (5), R^(a1) and R^(a8) denote the same as in theabove-mentioned formulae. R^(a11) is an alkyl group having 1 to 4carbons such as a methyl group, an ethyl group, a propyl group, or abutyl group, or a trialkylsilyl group, and r is 1 to 4.

Such compounds having an oxetane ring are described in detail inparagraph Nos. [0021] to [0084] of JP-A-2003-341217 above, and thecompounds described here may be suitably used in the present invention.

The oxetane compounds described in JP-A-2004-91556 can be used in thepresent invention. The details are described in paragraph Nos. [0022] to[0058].

Among the oxetane compounds used in the present invention, from theviewpoint of ink composition viscosity and tackiness, it is preferableto use a compound having one oxetane ring.

The ink composition of the present invention may comprise only one typeof cationically polymerizable compound or two or more types thereof incombination, but from the viewpoint of suppressing effectively shrinkageduring ink curing, it is preferable to use a combination of a vinylether compound and at least one type of compound selected from theoxetane compounds and the epoxy compounds.

The content of the cationically polymerizable compound in the inkcomposition is suitably in the range of 10 to 95 wt % relative to thetotal solids content of the composition, preferably 30 to 90 wt %, andmore preferably 50 to 85 wt %.

(a-2) Radically Polymerizable Compound

The radically polymerizable compound is a compound having a radicallypolymerizable ethylenically unsaturated bond, and may be any compound aslong as it has at least one radically polymerizable ethylenicallyunsaturated bond in the molecule; examples thereof include those havinga chemical configuration such as a monomer, an oligomer, or a polymer.One type of radically polymerizable compound may be used, or two or moretypes thereof may be used in combination in order to improve an intendedproperty. It is more preferable to use a polyfunctional compound havingtwo or more functional groups than it is to use a monofunctionalcompound. It is yet more preferable to use two or more types ofpolyfunctional compounds in combination in terms of controlling aspectsof performance such as reactivity or physical properties.

Examples of the polymerizable compound having a radically polymerizableethylenically unsaturated bond include unsaturated carboxylic acids suchas acrylic acid, methacrylic acid, itaconic acid, crotonoic acid,isocrotonoic acid, and maleic acid, and salts thereof, anhydrides havingan ethylenically unsaturated group, acrylonitrile, styrene, and varioustypes of radically polymerizable compounds such as unsaturatedpolyesters, unsaturated polyethers, unsaturated polyamides, andunsaturated urethanes.

Specific examples thereof include acrylic acid derivatives such as2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate,carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate,benzyl acrylate, bis(4-acryloxypolyethoxyphenyl)propane, neopentylglycoldiacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate,diethylene glycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, polyethylene glycol diacrylate,polypropylene glycol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate,trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate,oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, andepoxyacrylate; methacrylic derivatives such as methyl methacrylate,n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate,allyl methacrylate, glycidyl methacrylate, benzyl methacrylate,dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate,ethylene glycol dimethacrylate, triethylene glycol dimethacrylate,polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate,trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate,and 2,2-bis(4-methacryloxypolyethoxyphenyl)propane; and allyl compoundderivatives such as allyl glycidyl ether, diallyl phthalate, andtriallyl trimellitate. More specifically, commercial products, radicallypolymerizable or crosslinking monomers, oligomers, and polymers known inthe art such as those described in ‘Kakyozai Handobukku’ (CrosslinkingAgent Handbook), Ed. S. Yamashita (Taiseisha, 1981); ‘UV•EB KokaHandobukku’ (UV•EB Curing Handbook (Starting Materials) Ed. K. Kato(Kobunshi Kankoukai, 1985); ‘UV•EB Koka Gijutsu no Oyo to Shijyo’(Application and Market of UV•EB Curing Technology’, p. 79, Ed. Rad Tech(CMC, 1989); and E. Takiyama ‘Poriesuteru Jushi Handobukku’ (PolyesterResin Handbook), (The Nikkan Kogyo Shimbun Ltd., 1988) can be used.

It is preferable to use the radically polymerizable compound and thecationically polymerizable compound in combination since, due to highsensitivity characteristic of radical polymerization and low volumeshrinkage characteristic of cationic polymerization, a printed materialor a lithographic printing plate having both high sensitivity andadhesion is obtained.

(b) Polymerization Initiator

The ink composition of the present invention comprises a polymerizationinitiator. As the polymerization initiator, a known radicalpolymerization initiator or cationic polymerization initiator may beused, but it is preferable to use a radical polymerization initiator,and when a cationic polymerization initiator is used, it is preferableto use it in combination with a radical polymerization initiator. Thepolymerization initiators may be used singly or in a combination of twoor more types.

The radical polymerization initiator or the cationic polymerizationinitiator that can be used in the ink composition of the presentinvention is a compound that forms a polymerization initiating speciesby absorbing external energy. The external energy used for initiatingpolymerization is roughly divided into heat and actinic radiation, and athermal polymerization initiator and a photopolymerization initiator areused respectively. Examples of the actinic radiation include γ rays, βrays, an electron beam, UV rays, visible light, and IR rays. Thepolymerization initiator that can be used in the present invention ispreferably a radiation-sensitive radical polymerization initiator thatis sensitive to actinic radiation, that is, a so-called radicalphotopolymerization initiator.

(b-1) Radical Polymerization Initiator

Examples of the radical polymerization initiator that can be used in thepresent invention include (a) aromatic ketones, (b) aromatic onium saltcompounds, (c) organic peroxides, (d) thio compounds, (e)hexaarylbiimidazole compounds, (f) ketoxime ester compounds, (g) boratecompounds, (h) azinium compounds, (i) metallocene compounds, (j) activeester compounds, (k) compounds having a carbon-halogen bond, and (l)alkylamine compounds. These radical polymerization initiators may beused singly or in a combination of the above-mentioned compounds (a) to(l). The radical polymerization initiators of the present invention aresuitably used singly or in a combination of two or more types.

(b-2) Cationic Polymerization Initiator

As the cationic polymerization initiator (photo-acid generator) that canbe used in the present invention, for example, compounds that are usedfor chemically amplified photoresists or cationic photopolymerizationare used (ref. ‘Imejingu yo Yukizairyou’ (Organic Materials for Imaging)Ed. The Japanese Research Association for Organic Electronics Materials,Bunshin Publishing Co. (1993), pp. 187-192). Examples of the cationicpolymerization initiator suitably used in the present invention arelisted below.

Firstly, B(C₆F₅)₄ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, and CF₃SO₃ ⁻ salts ofaromatic onium compounds such as diazonium, ammonium, iodonium,sulfonium, and phosphonium can be cited. Secondly, sulfonates thatgenerate a sulfonic acid can be cited. Thirdly, halides thatphotogenerate a hydrogen halide can also be used. Fourthly, iron allenecomplexes can be cited.

(c) Coloring Agent

The coloring agent that can be used in the present invention is notparticularly limited, but a pigment and an oil-soluble dye that haveexcellent weather resistance and rich color reproduction are preferable,and it may be selected from any known coloring agent such as a solubledye. It is preferable that the coloring agent that can be suitably usedin the ink composition or the inkjet recording ink composition of thepresent invention does not function as a polymerization inhibitor in apolymerization reaction, which is a curing reaction. This is because thesensitivity of the curing reaction by actinic radiation should not bedegraded.

(c-1) Pigment

The pigment that can be used in the present invention is notparticularly limited and, for example, organic and inorganic pigmentshaving the numbers below described in the Color Index may be used.

That is, as a red or magenta pigment, Pigment Red 3, 5, 19, 22, 31, 38,43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1,81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149,166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, or 257,Pigment Violet 3, 19, 23, 29, 30, 37, 50, or 88, and Pigment Orange 13,16, 20, or 36; as a blue or cyan pigment, Pigment Blue 1, 15, 15:1,15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, or 60; as a greenpigment, Pigment Green 7, 26, 36, or 50; as a yellow pigment, PigmentYellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97,108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180,185, or 193; as a black pigment, Pigment Black 7, 28, or 26; as a whitepigment, Pigment White 6, 18, or 21, etc. may be used according to theintended application.

(c-2) Oil-Soluble Dye

The oil-soluble dye that can be used in the present invention isexplained below.

The oil-soluble dye that can be used in the present invention means adye that is substantially insoluble in water. Specifically, thesolubility in water at 25° C. (the mass of dye that can be dissolved in100 g of water) is no greater than 1 g, preferably no greater than 0.5g, and more preferably no greater than 0.1 g. Therefore, the oil-solubledye means a so-called water-insoluble pigment or an oil-soluble dye, andamong these the oil-soluble dye is preferable.

In the present invention, the oil-soluble dye may be used singly or in acombination of two or more types. Furthermore, another colorant such asa water-soluble dye, a disperse dye, or a pigment may be contained asnecessary in a range that does not interfere with the effects of thepresent invention.

Among the oil-soluble dyes that can be used in the present invention, asa yellow dye, any may be used. Examples thereof include aryl or heterylazo dyes having a coupling component such as a phenol, a naphthol, ananiline, a pyrazolone, a pyridone, or an open-chain active methylenecompound; azomethine dyes having a coupling component such as anopen-chain active methylene compound; methine dyes such as benzylidenedyes and monomethineoxonol dyes; quinone dyes such as naphthoquinonedyes and anthraquinone dyes; and other dye species such asquinophthalone dyes, nitro/nitroso dyes, acridine dyes, and acridinonedyes.

Among the above-mentioned oil-soluble dyes that can be used in thepresent invention, as a magenta dye, any may be used. Examples thereofinclude aryl or heteryl azo dyes having a coupling component such as aphenol, a naphthol, or an aniline; azomethine dyes having a couplingcomponent such as a pyrazolone or a pyrazolotriazole; methine dyes suchas arylidene dyes, styryl dyes, merocyanine dyes, and oxonol dyes;carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, andxanthene dyes; quinone dyes such as naphthoquinones, anthraquinones, oranthrapyridones; and condensed polycyclic dyes such as dioxazine dyes.

Among the oil-soluble dyes that can be used in the present invention, asa cyan dye, any may be used. Examples thereof include indoaniline dyes,indophenol dyes, and azomethine dyes having a coupling component such asa pyrrolotriazole; polymethine dyes such as cyanine dyes, oxonol dyes,and merocyanine dyes; carbonium dyes such as diphenylmethane dyes,triphenylmethane dyes, and xanthene dyes; phthalocyanine dyes;anthraquinone dyes; aryl or heteryl azo dyes having a coupling componentsuch as a phenol, a naphthol, or an aniline; and indigo/thioindigo dyes.

The above-mentioned dyes may be dyes that exhibit respective colors ofyellow, magenta, and cyan only after a part of the chromophoredissociates, and in that case the counter cation may be an inorganiccation such as an alkali metal or ammonium, may be an organic cationsuch as pyridinium or a quaternary ammonium salt, or may be a polymercation having the above cation as a partial structure.

Although not limited to the following, preferred specific examplesthereof include CI Solvent Black 3, 7, 27, 29, and 34; CI Solvent Yellow14, 16, 19, 29, 30, 56, 82, 93, and 162; CI Solvent Red 1, 3, 8, 18, 24,27, 43, 49, 51, 72, 73, 109, 122, 132, and 218; CI Solvent Violet 3; CISolvent Blue 2, 11, 25, 35, 38, 67, and 70; CI Solvent Green 3 and 7;and CI Solvent Orange 2. Particularly preferred examples thereof includeNubian Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, OilPink 312, Oil Red 5B, Oil Scarlet 308, Vali Fast Blue 2606, Oil Blue BOS(manufactured by Orient Chemical Industries, Ltd.), Aizen Spilon BlueGNH (manufactured by Hodogaya Chemical Co., Ltd.), Neopen Yellow 075,Neopen Magenta SE1378, Neopen Blue 808, Neopen Blue FF4012, and NeopenCyan FF4238 (manufactured by BASF).

In the present invention, a disperse dye may be used in a range thatenables it to be dissolved in a water-immiscible organic solvent.Specific preferred examples thereof include CI Disperse Yellow 5, 42,54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184:1, 186,198, 199, 201, 204, 224, and 237; CI Disperse Orange 13, 29, 31:1, 33,49, 54, 55, 66, 73, 118, 119, and 163; CI Disperse Red 54, 60, 72, 73,86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154,159, 164, 167:1, 177, 181, 204, 206, 207, 221, 239, 240, 258, 277, 278,283, 311, 323, 343, 348, 356, and 362; CI Disperse Violet 33; CIDisperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165:1,165:2, 176, 183, 185, 197, 198, 201, 214, 224, 225, 257, 266, 267, 287,354, 358, 365, and 368; and CI Disperse Green 6:1 and 9.

Particularly preferred examples of the oil-soluble dye include azo andazomethine dyes represented by Formulae (1) and (2) below. Dyesrepresented by Formula (2) below are known, in the photographic materialarea, as dyes that are generated from a coupler and a developing agentby oxidation.

In Formulae (1) and (2) above, R¹, R², R³ and R⁴ independently denote ahydrogen atom, a halogen atom, an aliphatic group, an aromatic group, aheterocyclic group, a cyano group, a hydroxyl group, a nitro group, anamino group, an alkylamino group, an alkoxy group, an aryloxy group, anamide group, an arylamino group, a ureido group, a sulfamoylamino group,an alkylthio group, an arylthio group, an alkoxycarbonylamino group, asulfonamide group, a carbamoyl group, a sulfamoyl group, a sulfonylgroup, an alkoxycarbonyl group, a heterocyclooxy group, an azo group, anacyloxy group, a carbamoyloxy group, a silyloxy group, anaryloxycarbonyl group, an aryloxycarbonylamino group, an imide group, aheterocyclothio group, a sulfinyl group, a phosphoryl group, an acylgroup, a carboxyl group, or a sulfo group.

In Formulae (1) and (2) above, in particular, R² is preferably, amongthe above-mentioned substituents, a hydrogen atom, a halogen atom, analiphatic group, an alkoxy group, an aryloxy group, an amide group, aureido group, a sulfamoylamino group, an alkoxycarbonylamino, or asulfonamide group.

In the present specification, the aliphatic group denotes an alkylgroup, a substituted alkyl group, an alkenyl group, a substitutedalkenyl group, an alkynyl group, a substituted alkynyl group, an aralkylgroup, or a substituted aralkyl group. The aliphatic group may have abranch or form a ring. The number of carbon atoms of the aliphatic groupis preferably 1 to 20, and more preferably 1 to 18. The aryl moiety ofthe aralkyl group and the substituted aralkyl group is preferably phenylor naphthyl, and particularly preferably phenyl. Examples of thesubstituents of the alkyl moieties of the substituted alkyl group, thesubstituted alkenyl group, the substituted alkynyl group, and thesubstituted aralkyl group include the substituents cited for explanationof R¹ to R⁴. Examples of the substituents of the aryl moiety of thesubstituted aralkyl group are the same as those of the substituent ofthe substituted aryl group below.

In the present specification, the aromatic group means an aryl group anda substituted aryl group. The aryl group is preferably phenyl ornaphthyl, and particularly preferably phenyl. The aryl moiety of thesubstituted aryl group is the same as that of the above-mentioned arylgroup. Examples of the substituent of the substituted aryl group includesubstituents cited for explanation of R¹ to R⁴.

In Formulae (1) and (2) above, A denotes —NR⁵R⁶ or a hydroxyl group, andR⁵ and R⁶ independently denote a hydrogen atom, an aliphatic group, anaromatic group, or a heterocyclic group. A is preferably —NR⁵R⁶. R⁵ andR⁶ may be bonded together to form a ring. R⁵ and R⁶ preferably eachdenote a hydrogen atom, an alkyl group, a substituted alkyl group, anaryl group, or a substituted aryl group, and most preferably a hydrogenatom, an alkyl group having 1 to 18 carbon atoms, or a substituted alkylgroup having 1 to 18 carbon atoms.

In Formula (2) above, B¹ denotes ═C(R³)— or ═N—, and B² denotes —C(R⁴)═or —N═. It is preferable that B¹ and B² are not —N=at the same time, andit is more preferable that B¹ is ═C(R³)— and B² is —C(R⁴)═. Any of R¹and R⁵, R³ and R⁶, and R¹ and R² may be bonded together to form anaromatic ring or a hetero ring.

In Formula (1) above, Y denotes an unsaturated heterocyclic group. Y ispreferably a five-membered or six-membered unsaturated hetero ring. Thehetero ring may be condensed with an aliphatic ring, an aromatic ring,or another hetero ring. Examples of the hetero atom of the hetero ringinclude N, O, and S.

Preferred examples of the above-mentioned unsaturated hetero ringinclude a pyrazole ring, an imidazole ring, a thiazole ring, anisothiazole ring, a thiadiazole ring, a thiophene ring, a benzothiazolering, a benzoxazole ring, a benzoisothiazole ring, a pyrimidine ring, apyridine ring, and a quinoline ring. It is also possible for theunsaturated heterocyclic group to have a substituent cited above as R¹to R⁴.

In Formula (2) above, X denotes a color photographic coupler residue.Preferred examples of the color photographic coupler residue are asfollows.

Yellow couplers: U.S. Pat. Nos. 3,933,501, 4,022,620, 4,326,024, and4,401,752, couplers represented by Formulae (I) and (II) in U.S. Pat.No. 4,248,961, JP-B-58-10739, GB Pat. Nos. 1,425,020 and 1,476,760, U.S.Pat. Nos. 3,973,968, 4,314,023, and 4,511,649, and EP Pat. Nos. 249,473Aand 502,424A; couplers represented by Formulae (1) and (2) in EP Pat.No. 513,496A (in particular, Y-28 on page 18); couplers represented byFormula (I) of claim 1 in EP Pat. No. 568,037A; couplers represented byFormula (1) of lines 45 to 55 in Column 1 in U.S. Pat. No. 5,066,576;couplers represented by Formula (I) in Paragraph 0008 in JP-A-4-274425;couplers of claim 1 on page 40 in EP Pat. No. 498,381A1 (in particular,D-35 on page 18); couplers represented by Formula (Y) on page 4 in EPPat. No. 447,969A1 (in particular, Y-1 (page 17) and Y-54 (page 41));and couplers represented by Formulae (II) to (IV) on lines 36 to 58 ofColumn 7 in U.S. Pat. No. 4,476,219 (in particular, II-17 and 19 (Column17), and II-24 (Column 19)).

Magenta couplers: U.S. Pat. Nos. 4,310,619 and 4,351,897, EP Pat. No.73,636, U.S. Pat. Nos. 3,061,432 and 3,725,067, Research Disclosure No.24220 (June, 1984) and No. 24230 (June, 1984), JP-A-60-33552,JP-A-60-43659, JP-A-61-72238, JP-A-60-35730, JP-A-55-118034,JP-A-60-185951, U.S. Pat. Nos. 4,500,630, 4,540,654, and 4,556,630,WO88/04795, JP-A-3-39737 (L-57 (page 11, lower right), L-68 (page 12,lower right), L-77 (page 13, lower right)), EP Pat. No. 456,257 [A-4]-63(p. 134), [A-4]-73, -75 (p. 139), EP Pat. No. 486,965 M-4, -6 (p. 26),M-7 (p. 27), EP Pat. No. 571,959A M-45 (p. 19), JP-A-5-204106 M-1 (p.6), and JP-A-4-362631 paragraph No. 0237, M-22, and U.S. Pat. Nos.3,061,432 and 3,725,067.

Furthermore, couplers described in JP-A-62-215272 (p. 91), JP-A-2-33144(p. 3 and 30), EP 355,660A (p. 4, 5, 45 and 47) are also useful.

Cyan coupler: U.S. Pat. Nos. 4,052,212, 4,146,396, 4,228,233, and4,296,200, EP Pat. No. 73,636, JP-A-4-204843, CX-1, 3, 4, 5, 11, 12, 14,15 (pp. 14 to 16); JP-A-4-43345 C-7, 10 (p. 35), 34, 35 (p. 37), (1-1),(1-17) (pp. 42 to 43); and couplers represented by Formula (Ia) or (Ib)of claim 1 in JP-A-6-67385.

Among the oil-soluble dyes represented by Formula (1) above, the magentadyes particularly preferably used are dyes represented by Formula (3)below.

In Formula (3) above, Z¹ denotes an electron-attracting group having aHammett substituent constant σp value of equal to or greater than 0.20.Z¹ is preferably an electron-attracting group having a σp value of atleast 0.30 but no greater than 1.0. Preferred specific examples of thesubstituent include electron-attracting substituents that are describedlater, and among them an acyl group having 2 to 12 carbons, an alkyloxycarbonyl group having 2 to 12 carbons, a nitro group, a cyano group, analkylsulfonyl group having 1 to 12 carbons, an arylsulfonyl group having6 to 18 carbons, a carbamoyl group having 1 to 12 carbons, and ahaloalkyl group having 1 to 12 carbons are preferable. A cyano group, analkylsulfonyl group having 1 to 12 carbons, and an arylsulfonyl grouphaving 6 to 18 carbons are particularly preferable, and a cyano group ismost preferable.

In Formula (3) above, Z² denotes a hydrogen atom, an aliphatic group, oran aromatic group.

In Formula (3) above, R¹ to R⁶ are the same as the corresponding ones ofFormula (1) above.

In Formula (3) above, Q denotes a hydrogen atom, an aliphatic group, anaromatic group, or a heterocyclic group. Among them, Q is preferably agroup formed from a group of non-metal atoms necessary to form a 5- to8-membered ring. Among them an aromatic group and a heterocyclic groupare particularly preferable. The 5- to 8-membered ring may besubstituted, may be a saturated ring, or may have an unsaturated bond.Preferred examples of the non-metal atom include a nitrogen atom, anoxygen atom, a sulfur atom, and a carbon atom. Specific examples of suchring structures include a benzene ring, a cyclopentane ring, acyclohexane ring, a cycloheptane ring, a cyclooctane ring, a cyclohexenering, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazinering, a triazine ring, an imidazole ring, a benzoimidazole ring, anoxazole ring, a benzoxazole ring, an oxane ring, a sulfolane ring, and athiane ring, and in a case where these rings have a further substituent,examples of the substituent include groups cited as examples ofsubstituents R¹ to R⁴ in Formula (1) above.

Preferred structures of the compounds represented by Formula (3) aboveare described in JP-A-2001-335714.

Among the dyes represented by Formula (2) above, the magenta dyeparticularly preferably employs a dye represented by Formula (4) below.

In Formula (4) above, G denotes a hydrogen atom, an aliphatic group, anaromatic group, a heterocyclic group, a cyano group, an alkoxy group, anaryloxy group, an alkylthio group, an arylthio group, an ester group, anamino group, a carbamoyl group, a sulfonyl group, a sulfamoyl group, aureido group, a urethane group, an acyl group, an amide group, or asulfonamide group.

In Formula (4) above, R¹, R², A, B¹, and B² are the same as thecorresponding ones of Formula (2) above, and preferred ranges are alsothe same.

In Formula (4) above, L denotes an atomic group forming a five-memberedor six-membered nitrogen-containing hetero ring, which may besubstituted with at least one of an aliphatic group, an aromatic group,a heterocyclic group, a cyano group, an alkoxy group, an aryloxy group,an alkylthio group, an arylthio group, an ester group, an amino group, acarbamoyl group, a sulfonyl group, a sulfamoyl group, a ureido group, aurethane group, an acyl group, an amide group, and a sulfonamide group,and this hetero ring may further form a condensed ring with anotherring.

With regard to compounds represented by Formula (4) above, A ispreferably —NR⁵R⁶, and L preferably forms a five-memberednitrogen-containing hetero ring; examples of the five-memberednitrogen-containing hetero ring include an imidazole ring, a triazolering, and a tetrazole ring.

Among the dyes represented by Formula (1) and Formula (2) above,compound examples (M0, M-1 to 6, a-21 to 25) for a magenta dye are shownbelow, but these are only for explaining the present invention indetail, and the present invention should not be construed as beinglimited thereto.

In the present invention, M0, M-4, M-6, or a-21 may be used, and M-4,M-6, and a-21 are particularly preferable.

TABLE 1

R₁ R₂ a-21

a-22

a-23

a-24

a-25

R₃ R₄ a-21

a-22

a-23

a-24

a-25

C₈H₁₇(t)

Other compound examples of the colorant that can be used in the presentinvention include those described in JP-A-2001-240763, 2001-181549, andJP-A-2001-335714, but the present invention should not be construed asbeing limited thereto.

The compound represented by Formula (3) above may be synthesized byreference to a method described in, for example, JP-A-2001-335714 orJP-A-55-161856. The compound represented by Formula (4) above may besynthesized by reference to a method described in, for example,JP-A-4-126772, JP-B-7-94180, or JP-A-2001-240763.

Among the dyes represented by Formula (2) above, as a cyan dye apyrrolotriazole azomethine dye represented by Formula (5) below isparticularly preferably used.

In Formula (5) above, A, R¹, R², B¹, and B² are the same as thecorresponding ones of Formula (2) above, and preferred ranges thereofare also the same.

In Formula (5) above, Z³ and Z⁴ are independently the same as G inFormula (4) above. Z³ and Z⁴ may be bonded together to form a ringstructure. One in which Z³ is an electron-attracting group having aHammett substituent constant σp value of equal to or greater than 0.30exhibits a sharp absorption and is more preferable. Moreover, one inwhich Z³ is an electron-attracting group having a Hammett substituentconstant σp value of equal to or greater than 0.45 is more preferable,and an electron-attracting group having a Hammett substituent constantσp value of equal to or greater than 0.60 is most preferable.Furthermore, one in which the sum of the Hammett substituent constant σpvalues of Z³ and Z⁴ is equal to or greater than 0.70 exhibits excellenthue of a cyancolor, and is more preferable.

In Formula (5) above, M is an atomic group forming a 1,2,4-triazole ringthat is condensed with the 5-membered ring of Formula (5) above; eitherone of the two atoms B³ and B⁴ at the sites of condensation with the5-membered ring is a nitrogen atom, and the other is a carbon atom.

The compound represented by Formula (5) above is preferably used as acyan dye, but it may be used as a magenta dye by changing a substituent.

The Hammett substituent constant σp value used in the presentspecification is now explained. The Hammett rule is an empirical ruleproposed by L. P. Hammett in 1935 in order to quantitatively deal withthe influence of a substituent on a reaction or equilibrium of a benzenederivative, and the validity thereof is currently widely recognized. Aσp value and a σm value are required for the substituent constant in theHammett rule, and details of these values can be referred to in manygeneral books, for example, ‘Lange's Handbook of Chemistry’, Ed. by J.A. Dean, 12th edition, 1979 (Mc Graw-Hill) or ‘Kagakuno Ryouiki’(Journal of Japanese Chemistry), special issue, 122, pp. 96 to 103, 1979(Nankodo Co., Ltd.). In the present invention, the substituents arelimited or explained using the Hammett substituent constant σp, but thisdoes not mean that they are limited to substituents whose values aredescribed in published references, and a substituent whose value is notpublished in the references but is included in the range if it ismeasured in accordance with the Hammett rule is of course included.Among Formulae (1) to (5) above, those that are not benzene derivativesare also included, but the σp value is used as a scale showing theelectronic effect of the substituent, irrespective of the position ofsubstitution. The σp value in the present invention is used with theabove-mentioned meaning.

Examples of electron-attracting groups having a Hammett substituentconstant σp value of equal to or greater than 0.60 include a cyanogroup, a nitro group, an alkylsulfonyl group (e.g. a methanesulfonylgroup), and an arylsulfonyl group (e.g. a benzenesulfonyl group).Examples of electron-attracting groups having a Hammett σp value ofequal to or greater than 0.45 include, in addition to the above, an acylgroup (e.g. an acetyl group), an alkoxycarbonyl group (e.g. adodecyloxycarbonyl group), an aryloxycarbonyl group (e.g.m-chlorophenoxycarbonyl), an alkylsulfinyl group (e.g.n-propylsulfinyl), an arylsulfinyl group (e.g. phenylsulfinyl), asulfamoyl group (e.g. N-ethylsulfamoyl, N,N-dimethylsulfamoyl), and ahaloalkyl group (e.g. trifluoromethyl).

Examples of electron-attracting groups having a Hammett substituentconstant σp value of equal to or greater than 0.30 include, in additionto the above, an acyloxy group (e.g. acetoxy), a carbamoyl group (e.g.N-ethylcarbamoyl, N,N-dibutylcarbamoyl), a haloalkoxy group (e.g.trifluoromethyloxy), a haloaryloxy group (e.g. pentafluorophenyloxy), asulfonyloxy group (e.g. a methylsulfonyloxy group), a haloalkylthiogroup (e.g. difluoromethylthio), an aryl group substituted with two ormore electron-attracting groups having a σp value of equal to or greaterthan 0.15 (e.g. 2,4-dinitrophenyl, pentachlorophenyl), and a hetero ring(e.g. 2-benzooxazolyl, 2-benzothiazolyl, 1-phenyl-2-benzimidazolyl).Specific examples of electron-attracting groups having a up value ofequal to or greater than 0.20 include, in addition to the above, ahalogen atom.

Furthermore, in the present invention, an oil-soluble dye represented byFormula (A-I) below can be used preferably.

In Formula (A-I): X₁, X₂, X₃, and X₄ independently denote a groupselected from —SO-Z, —SO₂-Z, —SO₂NR₁R₂, —CONR₁R₂, —CO₂R₁, and a sulfogroup. Here, Z denotes a substituted or unsubstituted alkyl group, asubstituted or unsubstituted cycloalkyl group, a substituted orunsubstituted alkenyl group, a substituted or unsubstituted aralkylgroup, a substituted or unsubstituted aryl group, or a substituted orunsubstituted heterocyclic group. R₁ and R₂ independently denote ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted cycloalkyl group, a substituted or unsubstitutedalkenyl group, a substituted or unsubstituted aralkyl group, asubstituted or unsubstituted aryl group, or a substituted orunsubstituted heterocyclic group, provided that R₁ and R₂ are not bothhydrogen atoms. M denotes a hydrogen atom, a metal element, a metaloxide, a metal hydroxide, or a metal halide. Y₁, Y₂, Y₃, and Y₄independently denote a hydrogen atom or a monovalent substituent. a₁ toa₄ and b₁ to b₄ denote the numbers of X₁ to X₄ and Y₁ to Y₄, andindependently denote an integer of 0 to 4, provided that the sum totalof a₁ to a₄ is equal to or greater than 2.

Among the oil-soluble dyes represented by Formula (A-I) above, anoil-soluble dye represented by Formula (A-II) below may particularlypreferably be used.

In Formula (A-II): X₁₁ to X₁₄, Y₁₁ to Y₁₈, and M are the same as X₁ toX₄, Y₁ to Y₄, and M in Formula (A-I) respectively. a₁₁ to a₁₄independently denote an integer of 1 or 2.

As a specific example of Formula (A-II) above, a compound example(AII-17) is cited, but this is for explaining the present invention indetail, and the present invention should not be construed as beinglimited thereto.

Compound No. M X a AII-17 Cu

1 AII-18 Cu

1 AII-19 Cu

1 AII-20 Cu

1 AII-21 Cu

1 AII-22 Cu

1 AII-23 Cu

1

In the present invention, it is preferable to use an oil-soluble dyehaving an oxidation potential that is more noble than 1.0 V (SCE). Themore noble the oxidation potential, the more preferable it is; it ismore preferable to use one having an oxidation potential more noble than1.1 V (SCE), and it is most preferable to use one having an oxidationpotential more noble than 1.2 V (SCE).

The oxidation potential value (Eox) can be easily measured by oneskilled in the art and a method therefor is described in, for example,P. Delahay, ‘New Instrumental Methods in Electrochemistry’, IntersciencePublishers (1954), A. J. Bard et al., ‘Electrochemical Methods’, JohnWiley & Sons (1980), and Akira Fujishima et al., ‘DenkikagakuSokuteihou’ (Electrochemical Measurement Methods), Gihodo Shuppan Sha(1984).

More specifically, a test sample is dissolved to give a concentration of1×10⁻⁴ to 1×10⁻⁶ mol/L in a solvent such as dimethylformamide oracetonitrile containing a supporting electrolyte such as sodiumperchlorate or tetrapropylammonium perchlorate, an oxidation wave whensweeping toward the oxidation side (noble side) using carbon (GC) as aworking electrode and a rotating platinum electrode as the counterelectrode using cyclic voltammetry or direct current polarographicequipment is approximated to a straight line, and the oxidationpotential of the midpoint of a line segment formed between anintersection point of the straight line and a residual current/potentialstraight line and an intersection point of the straight line and asaturated current straight line (or an intersection point with astraight line parallel to the ordinate passing through the potentialpeak value) is measured as a value relative to the SCE (saturatedcalomel electrode). This value sometimes deviates by on the order oftens of millivolts due to the effect of a liquid junction potential, theliquid resistance of the sample solution, or the like, but thereproducibility of the potential can be guaranteed by adding a standardsample (for example, hydroquinone). The support electrolyte and solventused may be selected appropriately according to the oxidation potentialand the solubility of the test sample. The support electrolyte andsolvent that can be used here may be referred to in Akira Fujishima etal., ‘Denkikagaku Sokuteihou’ (Electrochemical Measurement Methods),Gihodo Shuppan Sha (1984), pp. 101 to 118.

In the concentration range of the above-mentioned measurement solventand a phthalocyanine compound sample, the oxidation potential of adisassociated state is measured.

The value of Eox represents the ease of electron transfer from a sampleto an electrode; the larger the value (the more noble the oxidationpotential), the more difficult it is for electrons to transfer from thesample to the electrode, in other words, the more difficult it is tooxidize.

If a dye having a low oxidation potential is used, polymerization isgreatly inhibited by the dye, and the curability is degraded. When a dyehaving a noble oxidation potential is used, there is hardly anyinhibition of polymerization.

The coloring agent that can be used in the present invention ispreferably added to the ink composition or the inkjet recording inkcomposition of the present invention and then dispersed in the ink to anappropriate degree. For dispersion of the coloring agent, for example, adispersing machine such as a ball mill, a sand mill, an attritor, a rollmill, an agitator, a Henschel mixer, a colloidal mill, an ultrasonichomogenizer, a pearl mill, a wet type jet mill, or a paint shaker may beused.

When carrying out dispersion of the coloring agent, a dispersant may beadded. The type of dispersant is not particularly limited, but it ispreferable to use a polymeric dispersant, and examples of the polymericdispersant include the Solsperse series manufactured by Avecia.Furthermore, as a dispersion adjuvant, it is also possible to use asynergist, according to the various types of pigment. In the presentinvention, the dispersant and dispersion adjuvant are preferably addedat 1 to 50 parts by weight relative to 100 parts by weight of thepigment.

The coloring agent may be added directly to the ink composition of thepresent invention, but in order to improve dispersibility it may beadded in advance to a solvent or a dispersing medium such as apolymerizable compound used in the present invention. In the presentinvention, in order to avoid the problem of the solvent resistance beingdegraded when the solvent remains in the cured image and the VOC(Volatile Organic Compound) problem of the residual solvent, it ispreferable to add the coloring agent to a polymerizable compound. As apolymerizable compound used, it is preferable in terms of dispersionsuitability to select a monomer having the lowest viscosity.

In the present invention, it is preferable for the average particle sizeof the coloring agent to be in the range of 0.005 to 0.5 μm, morepreferably 0.01 to 0.45 μm, and yet more preferably, 0.015 to 0.3 μm.Furthermore, it is preferable for the maximum particle size of thecoloring agent to be 0.3 to 10 μm, and more preferably 0.3 to 3 μm. Itis preferable, in order to make the maximum particle size of the pigmentparticles be in the above-mentioned range, that the coloring agent, thedispersant, and the dispersing medium are selected, and dispersionconditions and filtration conditions are set. By such control ofparticle size, clogging of a head nozzle can be suppressed, and the inkstorage stability, the ink transparency, and the curing sensitivity canbe maintained, which is preferable.

(d) Fragrance

The ink composition of the present invention comprises a fragrance. Thefragrance is effective in reducing the odor of the ink composition.

The fragrance is preferably one that neutralizes or masks an odor,particularly one originating from a polymerizable compound.

As the fragrance, a known fragrance may be appropriately selected andused. One type of fragrance may be used on its own, or a plurality offragrances may be selected and used.

The fragrance is preferably appropriately selected according to apolymerizable compound or a solvent that is used in the ink composition,and it is preferably optimized by combining known fragrances.

As the fragrance, either a natural fragrance or a synthetic fragrancemay be used.

The natural fragrances may be divided roughly into animal-derivedfragrances and plant-derived fragrances. Examples of the animal-derivedfragrances include castoreum, musk, ambergris, and civet. Examples ofthe plant-derived fragrances include lemon oil, orange oil, lime oil,bergamot oil, eucalyptus oil, mandarin oil, wintergreen oil, camphoroil, houshou oil, oakmoss oil, opopanax oil, copaiba oil, sandalwoodoil, cedarwood oil, tolu balsam oil, benzoin oil, vanilla oil, abies firoil, almond oil, calamus oil, chamomile oil, cardamom oil, galbanum oil,caraway oil, cumin oil, coriander oil, juniper berry oil, spearmint oil,sage oil, celery oil, thyme oil, tarragon oil, nutmeg oil, basil oil,hyssop oil, petitgrain oil, buchu oil, pennyroyal oil, peppermint oil,mace oil, lavender oil, rosemary oil, lovage oil, laurel oil, amyrisoil, elemi oil, cassia oil, guaiac oil, clove oil, styrax oil, geraniumoil, tangerine oil, patchouli oil, vetiver oil, labdanum oil, lemongrass oil, angelica oil, cypress oil, hiba oil, citronella oil, anisseed oil, ylang-ylang oil, clary sage oil, cinnamon oil, star anis oil,cananga oil, blackcurrant oil, ambrette seed oil, bay oil, bois de roseoil, cajuput oil, cassie oil, coriander oil, costus oil, davana oil,dill oil, fennel oil, fenugreek oil, genet oil, grapefruit oil, gingeroil, hop oil, hyacinth oil, immortelle oil, jasmine oil, jonquil oil,lavandin oil, linaloe oil, litsea cubeba oil, marjoram oil, mimosa oil,myrrh oil, myrtle oil, narcissus oil, olibanum oil, orris oil, parsleyoil, palmarosa oil, pepper oil, perilla oil, neroli oil, orange floweroil, pimenta oil, pine oil, rose oil, spike lavender oil, taget oil,tonka bean oil, tuberose oil, terpene oil, valerian oil, violet oil,wormwood oil, and yuzu oil.

The natural fragrance component may be in any form such as an essentialoil, an absolute, a concrete, or a resinoid.

Furthermore, according to the intended application, a main component, acharacteristic component, or a necessary component may be a fractionatedfrom the above-mentioned natural fragrance, and used as a fractionatedfragrance. It may be separated and purified by distillation,recrystallization, chromatography, a chemical treatment, etc.

Synthetic fragrances are divided into fractionated fragrances obtainedby separating and purifying an effective component contained in a plantessential oil, and synthetic fragrances. The latter are produced by atotal synthetic method, a semisynthetic method, or a biosynthetic methodin an organic synthetic process using a petrochemical product or anatural terpene compound. Furthermore, among the synthetic fragrances,there are those that are chemically synthesized and are the same as aneffective component in a natural fragrance, and those that are new andhave not been found in a natural fragrance, but have an excellent aroma.

Focusing on the molecular structure of the fragrance, examples of thefragrance include hydrocarbons such as aliphatic hydrocarbons, terpenehydrocarbons, and aromatic hydrocarbons, alcohols such as aliphaticalcohols, terpene alcohols, and aromatic alcohols, ethers such asaliphatic ethers and aromatic ethers, oxides such as aliphatic oxidesand terpene oxides, aldehydes such as aliphatic aldehydes, terpene-basedaldehydes, alicyclic aldehydes, thioaldehydes, and aromatic aldehydes,ketones such as aliphatic ketones, terpene ketones, alicyclic ketones,aliphatic cycloketones, nonbenzenoid aromatic ketones, and aromaticketones, acetals, ketals, phenols, phenol ethers, acids such as fattyacids, terpene-based carboxylic acids, alicyclic carboxylic acids, andaromatic carboxylic acids, acid amides, lactones such as aliphaticlactones, macrocyclic lactones, terpene-based lactones, alicycliclactones, and aromatic lactones, esters such as aliphatic esters,furan-based carboxylic acid esters, aliphatic cyclocarboxylic acidesters, cyclohexyl carboxylic acid esters, terpene-based carboxylic acidesters, and aromatic carboxylic acid esters, and nitrogen-containingcompounds such as nitromusks, nitriles, amines, pyridines, quinolines,pyrrole, and indole.

Specific examples of the hydrocarbons include α-pinene, β-pinene,camphene, myrcene, limonene, terpinene, ocimeme, γ-terpinene,α-phellandrene, p-cymene, β-caryophyllene, β-farnesene,1,3,5-undecatriene, and diphenylmethane.

Examples of the alcohols include aliphatic alcohols, aromatic alcohols,and terpene alcohol compounds such as trans-2-hexenol, cis-3-hexenol,3-octanol, 1-octen-3-ol, 2,6-dimethyl-2-heptanol, 9-decenol,4-methyl-3-decen-5-ol, 10-undecenol, trans-2-cis-6-nonadienol, linalol,geraniol, nerol, citronellol, rhodinol, myrcenol, lavandulol,tetrahydrogeraniol, tetrahydrolinalol, hydroxycitronellol,dihydromyrcenol, allocymenol, α-terpineol, terpinen-4-ol, 1-menthol,borneol, isopulegol, norpol, farnesol, nerolidol, bisabolol, cedrol,patchouli alcohol, vetiverol, 2,4-dimethyl-3-cyclohexene-1-methanol,4-isopropylcyclohexanol, 4-isopropylcyclohexanemethanol,1-(4-isopropylcyclohexyl)ethanol,2,2-dimethyl-3-(3-methylphenyl)propanol, p-t-butylcyclohexanol,o-t-butylcyclohexanol, ambrinol, 1-(2-t-butylcyclohexyloxy)-2-butanol,pentamethylcyclohexylpropanol, 1-(2,2,6-trimethylcyclohexyl)-3-hexanol,benzyl alcohol, phenethyl alcohol, phenoxyethyl alcohol, styrallylalcohol, anis alcohol, cinnamic alcohol, phenylpropyl alcohol,dimethylbenzylcarbinol, dimethylphenylethylcarbinol,phenethylmethylethylcarbinol, 3-methyl-5-phenylpentanol, thymol,carvacrol, orcinol monomethyl ether, eugenol, isoeugenol, andpropenylguaetol.

Examples of the ethers include aliphatic ethers, aromatic ethers, andterpene oxide compounds such as nerol oxide, myroxide, 1,8-cineole, roseoxide, limetol, menthofuran, linanol oxide, butyldimethyldihydropyran,acetoxyamyltetrahydropyran, cedryl methyl ether, methoxycyclodecane,1-methyl-1-methoxycyclodecane, ethoxymethyl cyclododecyl ether,tricyclodecenyl methyl ether, rubofix, cedroxide, amboxane, grisalva,anisole, dimethylhydroquinone, paracresyl methyl ether, acetoanisole,anethole, dihydroanethole, estragole, diphenyl ether, methyleugenol,methylisoeugenol, benzylisoeugenol, phenylmethyl isoamyl ether,β-naphthylmethyl ether, β-naphthyl ethyl ether, β-naphthyl isobutylether, and hexamethylhexahydrocyclopentane benzopyran.

Examples of the aldehydes include aliphatic aldehydes, aromaticaldehydes, and terpene aldehyde compounds such as hexylaldehyde,heptylaldehyde, octylaldehyde, nonylaldehyde, decylaldehyde,undecylaldehyde, dodecylaldehyde, tridecylaldehyde,trimethylhexylaldehyde, methyloctylacetaldehyde,methylnonylacetaldehyde, trans-2-hexenal, cis-4-heptenal,2,6-nonadienal, cis-4-decenal, undecylene aldehyde, trans-2-dodecenal,trimethylundecenal, 2,6,10-trimethyl-5,9-undecadienal, citral,citronellal, hydroxycitronellal, perillaldehyde,methoxydihydrocitronellal, citronellyloxyacetaldehyde,2,4-dimethyl-3-cyclohexenylaldehyde, isocyclocitral, scentenal, myracaldehyde, lyral, vernaldehyde, dupical, maceal, boronal, cetonal,benzaldehyde, phenylacetaldehyde, phenylpropional, cinnamic aldehyde,α-amylcinnamic aldehyde, α-hexylcinnamic aldehyde, hydratropic aldehyde,anis aldehyde, p-methylphenylacetaldehyde, cuminaldehyde, cyclamenaldehyde, 3-(p-t-butylphenyl)propanal, p-ethyl-2,2-dimethylhydrocinnamicaldehyde, 2-methyl-3-(p-methoxyphenyl)propanal,p-t-butyl-α-methylhydrocinnamic aldehyde, salicylaldehyde, heliotropin,helional, vanillin, ethylvanillin, and methylvanillin.

Examples of the acetals include acetal compounds such as octanal glycolacetal, acetaldehyde ethyl-cis-3-hexenylacetal, citral dimethylacetal,citral diethyl acetal, acetaldehyde ethyl linalyl acetal,hydroxycitronellal dimethyl acetal, phenylacetaldehyde dimethyl acetal,hydratropic aldehyde dimethyl acetal, phenylacetaldehyde glycerylacetal, acetaldehyde phenylethyl ethyl acetal, acetaldehyde phenylethylpropyl acetal, phenylpropanal propylene glycol acetal,4,4,6-trimethyl-2-benzyl-1,3-dioxane,2,4,6-trimethyl-2-phenyl-1,3-dioxane,4,4,6-trimethyl-2-butyl-1,3-dioxane, tetrahydroindeno-m-dioxine,dimethyltetrahydroindeno-m-dioxine, and karanal.

Examples of the ketones include aliphatic ketones, aromatic ketones, andterpene ketone compounds such as acetone, diacetyl, methyl amyl ketone,ethyl amyl ketone, methyl hexyl ketone, methyl nonyl ketone,methylheptenone, corvone, camphor, carvone, menthone, d-pulegone,pepiritone, fention, geranyl acetone, cedryl methyl ketone, nootkatone,ionone, methylionone, allylionone, irone, damascone, damascenone,dynascone, maltol, ethylmaltol, 2,5-dimethyl-4-hydroxyfuranone,p-t-butylcyclohexanone, amylcyclopentanone, heptylcyclopentanone,dihydrojasmone, cis-jasmone, florex, plicatone, muscone, civetone,cyclopentadecanone, cyclohexadecenone,4-cyclohexyl-4-methyl-2-pentanone, p-menthel-6-yl-propanone,2,2,5-trimethyl-5-menthylcyclopentanone,ethoxyvinyltetramethylcyclohexanone, dihydropentamethylindanone,IsoESuper (product name), Trimofix (product name), acetophenone,p-methylacetophenone, benzylacetophenone, carone, raspberry ketone,anisil acetone, 4-(4-hydroxy-3-methoxyphenyl)-2-butanone, methylnaphthyl ketone, 4-phenyl-4-methyl-2-pentanone, benzophenone,6-acetylhexamethylindane, 4-acetyldimethyl-t-butylindane, 5-acetyltetramethylisopropylindane, and 6-acetylhexatetralin.

Examples of the esters include aliphatic esters, aromatic esters, andcarbonate compounds such as ethyl formate, cis-3-hexenyl formate,linalyl formate, citronellyl formate, geranyl formate, benzyl formate,phenylethyl formate, ethyl acetate, butyl acetate, isoamyl acetate,methyl cyclopentylideneacetate, hexyl acetate, cis-3-hexenyl acetate,trans-3-hexenyl acetate, isononyl acetate, citronellyl acetate,lavandulyl acetate, geranyl acetate, linalyl acetate, myrcenyl acetate,terpinyl acetate, menthyl acetate, menthanyl acetate, nopyl acetate,bornyl acetate, isobornyl acetate, p-t-butylcyclohexyl acetate,o-t-butylcyclohexyl acetate, tricyclodecenyl acetate,2,4-dimethyl-3-cyclohexene-1-methanyl acetate, benzyl acetate,phenylethyl acetate, styrallyl acetate, cinnamyl acetate, anisylacetate, p-cresyl acetate, heliotropyl acetate, guaiyl acetate, cedrylacetate, vetiveryl acetate, decahydro-β-naphthyl acetate, acetyleugenol,acetylisoeugenol, ethyl propionate, isoamyl propionate, citronellylpropionate, geranyl propionate, linalyl propionate, terpinyl propionate,benzyl propionate, cinnamyl propionate, allyl cyclohexylpropionate,tricyclodeqenyl propionate, ethyl butyrate, ethyl 2-methylbutyrate,butyl butyrate, isoamyl butyrate, hexyl butyrate, linalyl butyrate,geranyl butyrate, citronellyl butyrate, benzyl butyrate, cis-3-hexenylisobutyrate, citronellyl isobutyrate, geranyl isobutyrate, linalylisobutyrate, benzyl isobutyrate, phenylethyl isobutyrate, phenoxyethylisobutyrate, tricyclodecenyl isobutyrate, ethyl isovalerate, propylvalerate, citronellyl isovalerate, geranyl isovalerate, benzylisovalerate, cinnamyl isovalerate, phenylethyl isovalerate, ethylcaproate, allyl caproate, ethyl enanthate, allyl enanthate, ethylcaprate, citronellyl tiglate, methyl octynecarboxylate, allyl2-pentyloxyglycolate, cis-3-hexenylmethyl carbonate, ethyl pyruvate,isoamyl pyruvate, ethyl acetoacetate, ethyl levulinate, methyl benzoate,ethyl benzoate, isobutyl benzoate, isoamyl benzoate, benzyl benzoate,geranyl benzoate, linalyl benzoate, phenylethyl benzoate, methyldihydroxydimethylbenzoate, methyl phenylacetate, ethyl phenylacetate,isobutyl phenylacetate, isoamyl phenylacetate, geranyl phenylacetate,benzyl phenylacetate, phenylethyl phenylacetate, p-cresyl phenylacetate,methyl cinnamate, ethyl cinnamate, benzyl cinnamate, cinnamyl cinnamate,phenylethyl cinnamate, methyl salicylate, ethyl salicylate, isobutylsalicylate, isoamyl salicylate, hexyl salicylate, cis-3-hexenylsalicylate, benzyl salicylate, phenylethyl salicylate, methyl anisate,ethyl anisate, methyl anthranilate, ethyl anthranilate, methylmethylanthranilate, methyl jasmonate, methyl dihydrojasmonate, ethylmethylphenylglycidate, ethyl phenylglycidate, glycomer, fructone,fraistone, frutate, givescone, and karikisole (product name).

Examples of the carboxylic acids include carboxylic acid compounds suchas geranylic acid, citronellylic acid, benzoic acid, phenylacetic acid,phenylpropionic acid, cinnamic acid, and 2-methyl-2-pentenonic acid.

Examples of the lactones include aliphatic lactone and aromatic lactonecompounds such as γ-octalactone, γ-nonalactone, γ-decalactone,γ-undecalactone, δ-decalactone, coumarin, dihydrocoumarin, jasmolactone,jasmine lactone, sugar lactone, cyclopentadecanolide,cyclohexadecanolide, 12-cyclopentadecanolide, cyclohexadecenolide,12-oxa-16-hexadecanolide, 11-oxa-16-hexadecanolide,10-oxa-16-hexadecanolide, and ethylene dodecanedioate.

Examples of the nitrogen-containing compounds includenitrogen-containing compounds such as acetyl pyrrole, indole, skatole,indolene, 2-acetylpyridine, maritima, 6-methylquinoline,6-isopropylquinoline, 6-isobutylquinoline, 2-acetylpyrazine,2,3-dimethylpyrazine, 2-isopropyl-3-methoxypyrazine,2-isobutyl-3-methoxypyrazine, 2-sec-butyl-3-methoxypyrazine,trimethylpyrazine, geranyl nitrile, citronellyl nitrile,5-phenyl-3-methyl-2-pentene nitrile, 3,7-dimethyl-2,6-nonadiene nitrile,cinnamon nitrile, cumine nitrile, dodecane nitrile, tridecene-2-nitrile,and 5-methyl-3-heptanone oxime.

Among these, representative examples thereof include acetyl cedrene,IsoESuper (brand name), ethyl isovalerate, benzyl isovalerate,ethylvanillin, ethylene brassylate, 1-octen-3-ol, Galaxolide (brandname), camphor, methyl cinnamate, geraniol, geranyl acetate, benzylacetate, linalyl acetate, Sanderol (brand name), cyclamen aldehyde,cyclopentadecanolide, citral, citronellal, citronellol, methyldihydrojasmonate, cis-jasmine, damascone, terpiol, Tonalide (brandname), Bacdanol, vanillin, hydroxycitronellal, phenylacetaldehyde,2-phenylethanol, hexylcinnamic aldehyde, cis-3-hexenol, heliotropin,methyl atratrate, methyl ionone, menthol, ionone, linalol, Lyral (brandname), Kovanol (brand name), Lilial (brand name), and rose oxide.

Among these, it is preferable to use as the fragrance a terpene compoundsuch as a terpene hydrocarbon, a terpene alcohol, a terpene oxide, aterpene-based aldehyde, a terpene ketone, a terpene-based carboxylicacid, a terpene-based lactone, or a terpene-based carboxylic acid esterand/or an ester compound such as an aliphatic ester, a furan-basedcarboxylic acid ester, an aliphatic cyclocarboxylic acid ester, acyclohexyl carboxylic acid ester, a terpene-based carboxylic acid ester,or an aromatic carboxylic acid ester.

A fragrance for an acrylic odor is explained in detail below.

An acrylic acid ester monomer and a methacrylic acid ester monomer areimportant starting materials in the ink composition, but have an acrylicodor. These starting materials give the odor if even a trace amount (100ppb) remains after the ink composition is discharged by inkjet and curedby exposure to light.

It is possible to reduce the acrylic odor by adding to the inkcomposition and the cured ink, particularly those having this kind ofacrylic odor:

fragrances of group A: at least one type of fragrance selected from thegroup consisting of fragrances having an orange note,

fragrances of group B: at least one type of fragrance selected from thegroup consisting of fragrances having a green note.

Examples of the fragrance selected from the fragrances having an orangenote (group A) include Valencia orange oil, bergamot oil, neroli oil,petitgrain oil, d-limonene, linalol, orange flower absolute, linalylacetate, methyl anthranilate auranthiol, methyl beta-naphthyl ketone,and yara yara, these may be used singly or as a mixture of two or moretypes thereof, and Valencia orange oil and bergamot oil are particularlypreferable. The mixing ratio of the fragrance relative to the totalamount of the ink composition is preferably 0.001 to 2.0 mass %(hereinafter, simply called ‘%’), and more preferably 0.005% to 1.0%.

Examples of the fragrance selected from the fragrances having a greennote (group B) include cis-3-hexenol, cis-3-hexenyl acetate,phenylacetaldehyde, dimethyltetrahydrobenzaldehyde, methylphenylcarbinylacetate, methyloctine carbonate, allyl butyrate, cuminaldehyde,allylcyclohexyloxy acetate, butylorthobutylglycolate, pyrazine, andethyl benzoate. They may be used singly or as a mixture of two or moretypes, and cis-3-hexenol, cis-3-hexenyl acetate, phenylacetaldehyde,dimethyltetrahydrobenzaldehyde, methylphenylcarbinyl acetate, andmethyloctine carbonate are particularly preferable. These green notesare due to a fragrance component that is also present in naturalfragrances such as rose, geranium, and violet leaf, but the origin isnot particularly limited. The mixing ratio of the fragrance in anexternal preparation (formulation, etc.) is the same as for the group offragrances having an orange note, is preferably 0.001% to 2.0% relativeto the total amount of the external preparation, and more preferably0.005% to 1.0%.

When the mixing ratio of the fragrance of each of group A and group B isless than 0.001%, a sufficient masking effect cannot be obtained,whereas if each thereof exceeds 2.0%, although the masking effect can beobtained sufficiently, the aroma of the fragrance is too strong and isnot desirable for practical use. Furthermore, the ratio by mass of thefragrance of group A and the fragrance of group B (fragrance of groupA:fragrance of group B) is preferably 150:1 to 1:1, and more preferably100:1 to 1:1. If the ratio by mass is less than 100:1, the maskingeffect is not sufficient, and if it exceeds 1:1, the balance of theodors becomes poor.

In the present invention, the role of the fragrance in the actual inkcomposition should be to impart palatability in addition to masking,that is, neutralizing the acrylic odor. It is therefore possible tofreely use the above-mentioned fragrance components known in the artother than the fragrance having an orange note of group A and thefragrance having a green note of group B.

(2) Optional Component

(e) Sensitizing Dye

The ink composition of the present invention may contain a sensitizingdye in order to promote decomposition of the above-mentionedpolymerization initiator by absorbing specific actinic radiation, inparticular when used for inkjet recording. The sensitizing dye absorbsspecific actinic radiation and attains an electronically excited state.The sensitizing dye in the electronically excited state causes actionssuch as electron transfer, energy transfer, or heat generation uponcontact with the polymerization initiator. This causes thepolymerization initiator to undergo a chemical change and decompose,thus forming a radical, an acid, or a base.

Preferred examples of the sensitizing dye include those that belong tocompounds below and have an adsorption wavelength in the region of 350nm to 450 nm.

Polynuclear aromatic compounds (e.g. pyrene, perylene, triphenylene),xanthenes (e.g. fluorescein, eosin, erythrosine, rhodamine B, rosebengal), cyanines (e.g. thiacarbocyanine, oxacarbocyanine), merocyanines(e.g. merocyanine, carbomerocyanine), thiazines (e.g. thionine,methylene blue, toluidine blue), acridines (e.g. acridine orange,chloroflavin, acriflavine), anthraquinones (e.g. anthraquinone),squaryliums (e.g. squarylium), and coumarins (e.g.7-diethylamino-4-methylcoumarin).

Preferred examples of the sensitizing dye include compounds representedby Formulae (IX) to (XIII) below.

In Formula (IX), A¹ denotes a sulfur atom or NR⁵⁰, R⁵⁰ denotes an alkylgroup or an aryl group, L² denotes a non-metallic atomic group forming abasic nucleus of a dye in cooperation with a neighboring A¹ and theneighboring carbon atom, R⁵¹ and R⁵² independently denote a hydrogenatom or a monovalent non-metallic atomic group, and R⁵¹ and R⁵² may bebonded together to form an acidic nucleus of a dye. W denotes an oxygenatom or a sulfur atom.

In Formula (X), Ar¹ and Ar² independently denote an aryl group and areconnected to each other via a bond of -L³-. Here, L³ denotes —O— or —S—.W has the same meaning as that shown in Formula (IX).

In Formula (XI), A₂ denotes a sulfur atom or NR⁵⁹, L⁴ denotes anon-metallic atomic group forming a basic nucleus of a dye incooperation with the neighboring A₂ and carbon atom, R⁵³, R⁵⁴, R⁵⁵, R⁵⁶,R⁵⁷, and R⁵⁸ independently denote a monovalent non-metallic atomicgroup, and R⁵⁹ denotes an alkyl group or an aryl group.

In Formula (XII), A³ and A⁴ independently denote —S—, —NR⁶²—, or —NR⁶³—,R⁶² and R⁶³ independently denote a substituted or unsubstituted alkylgroup, or a substituted or unsubstituted aryl group, L⁵ and L⁶independently denote a non-metallic atomic group forming a basic nucleusof a dye in cooperation with the neighboring A³ and A⁴ and neighboringcarbon atom, and R⁶⁰ and R⁶¹ independently denote a hydrogen atom or amonovalent non-metallic atomic group, or are bonded to each other toform an aliphatic or aromatic ring.

In Formula (XIII), R⁶⁶ denotes an aromatic ring or a hetero ring, whichmay have a substituent, and A⁵ denotes an oxygen atom, a sulfur atom, or—NR⁶⁷—. R⁶⁴, R⁶⁵, and R⁶⁷ independently denote a hydrogen atom or amonovalent non-metallic atomic group, and R⁶⁷ and R⁶⁴, and R⁶⁵ and R⁶⁷may be bonded to each other to form an aliphatic or aromatic ring.

Specific examples of the compounds represented by Formulae (IX) to(XIII) include those listed below.

(f) Cosensitizer

The ink composition of the present invention preferably comprises acosensitizer. In the present invention, the cosensitizer has thefunction of further improving the sensitivity of the sensitizing dye toactinic radiation or the function of suppressing inhibition by oxygen ofpolymerization of a polymerizable compound, etc.

Examples of such a cosensitizer include amines such as compoundsdescribed in M. R. Sander et al., ‘Journal of Polymer Society’, Vol. 10,p. 3173 (1972), JP-B-44-20189, JP-A-51-82102, JP-A-52-134692,JP-A-59-138205, JP-A-60-84305, JP-A-62-18537, JP-A-64-33104, andResearch Disclosure No. 33825, and specific examples thereof includetriethanolamine, ethyl p-dimethylaminobenzoate, p-formyldimethylaniline,and p-methylthiodimethylaniline.

Other examples of the cosensitizer include thiols and sulfides such asthiol compounds described in JP-A-53-702, JP-B-55-500806, andJP-A-5-142772, and disulfide compounds of JP-A-56-75643, and specificexamples thereof include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole,2-mercaptobenzimidazole, 2-mercapto-4(3H)-quinazoline, andβ-mercaptonaphthalene.

Yet other examples of the cosensitizer include amino acid compounds(e.g. N-phenylglycine, etc.), organometallic compounds described inJP-B-48-42965 (e.g. tributyltin acetate, etc.), hydrogen-donatingcompounds described in JP-B-55-34414, sulfur compounds described inJP-A-6-308727 (e.g. trithiane, etc.), and phosphorus compounds describedin JP-A-6-250387 (diethylphosphite, etc.).

(g) Other Components

The ink composition of the present invention may comprise othercomponents as necessary. Examples of the other components includeradical polymerization inhibitors, cationic polymerization inhibitors,and solvents.

The radical polymerization inhibitor and the cationic polymerizationinhibitor may be added from the point of view of enhancing the storagestability. When the ink composition of the present invention is used asan inkjet recording ink composition, it is preferably heated in therange of 40° C. to 80° C. to thus make it less viscous and thendischarged, and in order to prevent clogging of a head due to thermalpolymerization it is preferable to add a polymerization inhibitor. Thepolymerization inhibitor is preferably added at 200 to 20,000 ppmrelative to the total amount of the ink composition of the presentinvention. Examples of the radical polymerization inhibitor includehydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and AIcupferron. The cationic polymerization inhibitor is a basicnitrogen-containing compound, and preferably a compound having atertiary amine structure. These compounds preferably have a pKa value of4 or greater, more preferably 5 or greater, and yet more preferably 7 to13, and preferred examples thereof include aliphatic amines, aromaticamines, and nitrogen-containing heterocyclic compounds having a pKa inthe above range.

While taking into consideration the ink composition and the inkjetrecording ink composition of the present invention being radiationcuring type ink compositions, it is preferable for them not to containany solvent so that the ink compositions can react quickly and be curedimmediately after landing. However, as long as the curing speed, etc. ofthe ink composition is not affected, a specified solvent may be added.In the present invention, as a solvent, an organic solvent or water maybe used. In particular, the organic solvent may be added in order toimprove the adhesion to a recording medium (a support such as paper).Adding an organic solvent having a high boiling point is effective sincethe problem with VOC can be avoided. The amount of organic solvent ispreferably 0.1 to 5 wt % relative to the total amount of the inkcomposition of the present invention, and more preferably 0.1 to 3 wt %.

As means for preventing the sensitivity from being degraded by a lightblocking effect of the coloring agent, which may be added to the inkcomposition, a combination of a cationically polymerizable compound anda cationic polymerization initiator, a combination of a radicallypolymerizable compound and a radical polymerization initiator, or aradical/cationic hybrid curing ink combining a polymerizable compoundand a polymerization initiator may be employed.

In addition to the above, the ink composition of the present inventionmay contain a known compound as necessary. Examples thereof include asurfactant (cationic, anionic, nonionic, fluorine-based, silicon-based),a leveling additive, a matting agent and, for adjusting film physicalproperties, a polyester resin, polyurethane resin, vinyl resin, acrylicresin, rubber resin, or wax, which may be appropriately selected andadded. Furthermore, in order to improve the adhesion to a recordingmedium such as a polyolefin or PET, a tackifier that does not inhibitpolymerization is preferably added. Specific examples of the tackifierinclude high molecular weight tacky polymers described on pp. 5 and 6 ofJP-A-2001-49200 (e.g. a copolymer formed from an ester of (meth)acrylicacid and an alcohol having an alkyl group with 1 to 20 carbons, an esterof (meth)acrylic acid and an alicyclic alcohol having 3 to 14 carbons,or an ester of (meth)acrylic acid and an aromatic alcohol having 6 to 14carbons), and a low molecular weight tackifying resin having apolymerizable unsaturated bond.

(3) Properties of Ink Composition

With regard to the ink composition of the present invention, thepolymerizable compound is preferably 1 to 97 wt %, and more preferably30 to 95 wt %, the polymerization initiator is preferably 0.01 to 20 wt%, and more preferably 0.1 to 20 wt %, the coloring agent is preferably1 to 10 wt %, and more preferably 2 to 8 wt %, and each component iscontained so that the total of each component expressed as wt %desirably becomes 100 wt %.

When the ink composition thus obtained is used for inkjet recording,while taking into consideration dischargability, the viscosity of theink composition at the discharge temperature (e.g. 25° C. to 80° C., andpreferably 25° C. to 50° C.) is preferably 5 to 30 mPa·s, and morepreferably 7 to 15 mPa·s. For example, the ink composition of thepresent invention has a viscosity at room temperature (25° C. to 30° C.)of preferably 8 to 300 mPa·s, and more preferably 10 to 100 mPa·s. Withregard to the ink composition of the present invention, it is preferablethat its component ratio is appropriately adjusted so that the viscosityis in the above-mentioned range. When the viscosity at room temperatureis set to be high, even when a porous recording medium is used,penetration of the ink into the recording medium can be prevented,uncured monomer can be reduced, and the odor can be reduced.Furthermore, ink spreading when ink droplets have landed can besuppressed, and as a result there is the advantage that the imagequality is improved. When the viscosity at room temperature is set to below, since it is unnecessary to heat the ink when discharging or it ispossible to set the heating temperature at a relatively low temperature,there are the advantages that the load on inkjet equipment becomes smalland the choice of inkjet heads that can be used is widened.

The surface tension of the ink composition of the present invention ispreferably 20 to 30 mN/m, and yet more preferably 23 to 28 mN/m. Whenrecording is carried out on various types of recording medium such aspolyolefin, PET, coated paper, and uncoated paper, from the viewpoint ofspread and penetration, it is preferably at least 20 mN/m, and from theviewpoint of wettability it is preferably not more than 30 mN/m.

(4) Inkjet Recording Method and Equipment

The ink composition of the present invention is preferably used forinkjet recording.

An inkjet recording method that can be suitably employed in the presentinvention is explained below.

(4-1) Inkjet Recording Method

The present invention provides a method for forming an image bydischarging the above-mentioned ink composition onto a recording medium(support, recording material, etc.) and curing the ink composition byirradiating the ink composition so discharged onto the recording mediumwith actinic radiation. That is, the present invention relates to aninkjet recording method comprising:

(a) a step of discharging an ink composition onto a recording medium;and

(b) a step of curing the ink composition by irradiating the inkcomposition so discharged with actinic radiation,

wherein the ink composition is the ink composition of the presentinvention.

The cured ink composition forms an image on the recording medium.

The peak wavelength of the actinic radiation is preferably 200 to 600nm, more preferably 300 to 450 nm, and yet more preferably 350 to 420nm. The output of the actinic radiation is preferably no greater than2,000 mJ/cm², and is more preferably 10 to 2,000 mJ/cm², yet morepreferably 20 to 1,000 mJ/cm², and particularly preferably 50 to 800mJ/cm².

The inkjet recording method of the present invention is explained bytaking as an example a process for producing a lithographic printingplate, the process comprising discharging an ink composition onto thelithographic printing plate so as to form an image.

A process for producing a lithographic printing plate of the presentinvention comprises:

(a) a step of discharging the ink composition of the present inventiononto a hydrophilic support, and

(b) a step of irradiating the discharged ink composition with radiationso as to cure the ink composition, thus forming a hydrophobic image onthe hydrophilic support by curing the ink composition.

(4-1-1) Hydrophilic Support Used for Lithographic Printing Plate

The lithographic printing plate comprises a support and an image formedon the support.

Conventionally, as the lithographic printing plate, a so-called PS platein which an oleophilic photosensitive resin layer is provided on ahydrophilic support has been widely used. In a process for producingthis PS plate, normally, after a mask exposure (surface exposure) iscarried out via a lith film, non-exposed areas are dissolved and removedto give a desired printing plate. However, in recent years, a techniqueof digitizing image information using a computer by electronicallyprocessing, storing, and outputting the information has becomewidespread, and a new image output system that can be used for the abovetechnique has been desired. In particular, a computer to plate (CTP)technique in which a printing plate is directly produced by scanningaccording to digitized image information with highly coherent light suchas laser light without using a lith film has been developed.

As a system for obtaining a lithographic printing plate that makespossible the above scanning exposure, a process for directly producing alithographic printing plate using an ink composition or an inkjetrecording ink composition can be cited. This process involves obtaininga printing plate having a desired image (preferably a hydrophobic image)by discharging an ink onto a support, and preferably a hydrophilicsupport, using an inkjet system, etc., and exposing this to actinicradiation so as to expose an area with the ink composition or the inkjetrecording ink to light. The ink composition or the inkjet recording inksuitable for such a system is the ink composition or the inkjetrecording ink of the present invention.

The support (recording medium) onto which the ink composition or theinkjet recording ink composition of the present invention is dischargedis not particularly limited, and a dimensionally stable sheet-formsupport may be used. The support is preferably a hydrophilic support.The support used in the lithographic printing plate of the presentinvention is not particularly limited, and a dimensionally stablesheet-form support may be used. It is preferable that a material formingthe support has a hydrophilic surface. Examples of materials forming thesupport include paper, paper laminated with a plastic (e.g.polyethylene, polypropylene, polystyrene, etc.), a metal sheet (e.g.aluminum, zinc, copper, etc.), a plastic film (e.g. cellulose diacetate,cellulose triacetate, cellulose propionate, cellulose butyrate,cellulose acetate butyrate, cellulose nitrate, polyethyleneterephthalate, polyethylene, polystyrene, polypropylene, polycarbonate,polyvinyl acetal, etc.), and paper or plastic film on which theabove-mentioned metal is laminated or vapor-deposited. Preferredexamples of the support include a polyester film and aluminum sheet.Among these, aluminum sheet is particularly preferable since thedimensional stability is good and it is relatively inexpensive.

The aluminum sheet is a pure aluminum sheet, an alloy sheet containingaluminum as a main component and a small amount of a different element,or a thin film of aluminum or an aluminum alloy laminated with aplastic. Examples of the different element contained in the aluminumalloy include silicon, iron, manganese, copper, magnesium, chromium,zinc, bismuth, nickel, and titanium. The content of the differentelement in the alloy is preferably equal to or less than 10 wt %. In thepresent invention, a pure aluminum sheet is preferable, but since it isdifficult to produce completely pure aluminum because of the refiningtechnique, a trace amount of a different element may be contained. Thecomposition of the aluminum sheet is not specified, and a knowngenerally used material may be utilized as appropriate.

The support preferably has a thickness of 0.1 to 0.6 mm, and morepreferably 0.15 to 0.4 mm.

Prior to the aluminum sheet being used, it is preferably subjected to asurface treatment such as a surface roughening treatment or an anodizingtreatment. Surface treatment makes it easy to improve the hydrophilicityand ensure that there is good adhesion between an image recording layerand the support. Prior to the aluminum sheet being subjected to thesurface roughening treatment, it may be subjected as desired to adegreasing treatment using a surfactant, an organic solvent, an aqueousalkaline solution, etc. in order to remove rolling oil on the surface.

The surface roughening treatment for the aluminum sheet surface may becarried out by various types of methods, and examples thereof include amechanical surface roughening treatment, an electrochemical surfaceroughening treatment (a surface roughening treatment involvingdissolving the surface electrochemically), and a chemical surfaceroughening treatment (a surface roughening treatment involvingselectively dissolving the surface chemically).

As a method for the mechanical surface roughening treatment, a knownmethod such as a ball grinding method, a brush grinding method, a blastgrinding method, or a buff grinding method may be used. It is alsopossible to use a transfer method in which an irregular shape istransferred using a roller provided with irregularities in an aluminumrolling stage.

As a method for the electrochemical surface roughening treatment, forexample, a method in which alternating current or direct current isapplied in an electrolyte solution containing an acid such ashydrochloric acid or nitric acid can be cited. It is also possible toemploy a method as described in JP-A-54-63902 in which a mixed acid isused.

The aluminum sheet subjected to a surface roughening treatment issubjected as necessary to an alkali etching treatment using an aqueoussolution of potassium hydroxide, sodium hydroxide, etc.; furthermore,after neutralization, it may be subjected to an anodizing treatment asdesired in order to improve the abrasion resistance.

As an electrolyte that may be used for the anodizing treatment of thealuminum sheet, various types of electrolytes that form a porous oxidefilm may be used. In general, sulfuric acid, hydrochloric acid, oxalicacid, chromic acid, or a mixed acid thereof may be used. Theconcentration of the electrolyte may be determined as appropriateaccording to the type of electrolyte.

Conditions for the anodizing treatment depend on the type of electrolyteused and cannot be specified, but in general the electrolyte solutionconcentration is 1 to 80 wt %, the solution temperature is 5° C. to 70°C., the current density is 5 to 60 A/dm², the voltage is 1 to 100V, andthe electrolysis time is 10 sec. to 5 min. The amount of anodized filmformed is preferably 1.0 to 5.0 g/m², and more preferably 1.5 to 4.0g/m². It is preferable for it to be in this range since good plate lifeand good scratch resistance of a non-image area of a lithographicprinting plate can be obtained.

As the support that can be used in the present invention, a substratethat has been subjected to the above-mentioned surface treatment and hasan anodized film may be used as it is, but in order to further improvethe adhesion to an upper layer, and the hydrophilicity, thecontamination resistance, the thermal insulation, etc., the substratemay appropriately be subjected as necessary to a treatment for enlargingmicropores of the anodized film, a sealing treatment, or a surfacehydrophilization treatment involving immersion in an aqueous solutioncontaining a hydrophilic compound, which are described inJP-A-2001-253181 or JP-A-2001-322365. These enlarging and sealingtreatments are not limited to those described therein, and anyconventionally known methods may be employed.

Sealing Treatment

The sealing treatment may be vapor sealing, a treatment with an aqueoussolution containing an inorganic fluorine compound such as a singletreatment with fluorozirconic acid or a treatment with sodium fluoride,vapor sealing with added lithium chloride, or a sealing treatment withhot water.

Among these, the sealing treatment with an aqueous solution containingan inorganic fluorine compound, the sealing treatment with vapor, andthe sealing treatment with hot water are preferable. Each thereof isexplained below.

Sealing Treatment with Aqueous Solution Containing Inorganic FluorineCompound

In the sealing treatment with an aqueous solution containing aninorganic fluorine compound, a metal fluoride can suitably be used asthe inorganic fluorine compound.

Specific examples thereof include sodium fluoride, potassium fluoride,calcium fluoride, magnesium fluoride, sodium fluorozirconate, potassiumfluorozirconate, sodium fluorotitanate, potassium fluorotitanate,ammonium fluorozirconate, ammonium fluorotitanate, potassiumfluorotitanate, fluorozirconic acid, fluorotitanic acid,hexafluorositicic acid, nickel fluoride, iron fluoride, fluorophosphoricacid, and ammonium fluorophosphate. Among them, sodium fluorozirconate,sodium fluorotitanate, fluorozirconic acid, and fluorotitanic acid arepreferable.

The concentration of the inorganic fluorine compound in the aqueoussolution is preferably at least 0.01 wt % from the viewpoint of sealingof micropores on an anodized coating being carried out sufficiently, andmore preferably at least 0.05 wt %, and it is preferably no greater than1 wt % from the viewpoint of contamination resistance, and morepreferably no greater than 0.5 wt %.

The aqueous solution containing an inorganic fluorine compoundpreferably further contains a phosphate compound. It is preferable for aphosphate compound to be contained since the hydrophilicity of thesurface of the anodized coating improves and the machine developabilityand the contamination resistance can be improved.

Preferred examples of the phosphate compound include phosphates of ametal such as an alkali metal or an alkaline earth metal.

Specific examples thereof include zinc phosphate, aluminum phosphate,ammonium phosphate, ammonium phosphate dibasic, ammonium dihydrogenphosphate, potassium dihydrogen phosphate, potassium phosphate dibasic,calcium phosphate, ammonium sodium hydrogen phosphate, magnesiumhydrogen phosphate, magnesium phosphate, ferrous phosphate, ferricphosphate, sodium dihydrogen phosphate, sodium phosphate, sodiumphosphate dibasic, lead phosphate, diammonium phosphate, calciumdihydrogen phosphate, lithium phosphate, phosphotungstic acid, ammoniumphosphotungstate, sodium phosphotungstate, ammonium phosphomolybdate,sodium phosphomolybdate, sodium phosphite, sodium tripolyphosphate, andsodium pyrophosphate. Among these, sodium dihydrogen phosphate, sodiumphosphate dibasic, potassium dihydrogen phosphate, and potassiumphosphate dibasic are preferable.

The combination of the inorganic fluorine compound and the phosphatecompound is not particularly limited, but the aqueous solutionpreferably comprises at least sodium fluorozirconate as the inorganicfluorine compound and at least sodium dihydrogen phosphate as thephosphate compound.

The concentration of the phosphate compound in the aqueous solution ispreferably at least 0.01 wt % from the viewpoint of improving machinedevelopability and contamination resistance, and more preferably atleast 0.1 wt %, and it is preferably no greater than 20 wt % from theviewpoint of solubility, and more preferably no greater than 5 wt %.

The proportion of each compound in the aqueous solution is notparticularly limited, but the ratio by weight of the inorganic fluorinecompound and the phosphate compound is preferably 1/200 to 10/1, andmore preferably 1/30 to 2/1.

Furthermore, the temperature of the aqueous solution is preferably atleast 20° C., and more preferably at least 40° C., and it is preferablyno higher than 100° C., and more preferably no higher than 80° C.

Moreover, the pH of the aqueous solution is preferably at least 1, andmore preferably at least 2, and it is preferably no greater than 11, andmore preferably no greater than 5.

A method for the sealing treatment with the aqueous solution containingan inorganic fluorine compound is not particularly limited and, forexample, an immersion method and a spray method may be used. They may beemployed once or a plurality of times, or in a combination of two ormore types.

Among these, the immersion method is preferable. When the treatment iscarried out by the immersion method, the treatment time is preferably atleast 1 sec., and more preferably at least 3 sec., and it is preferablyno greater than 100 sec., and more preferably no greater than 20 sec.

Sealing Treatment with Steam

With regard to the sealing treatment with steam, for example, a methodin which an anodized coating is contacted with steam at high pressure ornormal pressure continuously or discontinuously can be cited.

The temperature of the steam is preferably at least 80° C., and morepreferably at least 95° C., and it is preferably no greater than 105° C.

The pressure of the steam is preferably in the range of (atmosphericpressure−50 mmAq) to (atmospheric pressure+300 mmAq) (1.008×10⁵ to1.043×10⁵ Pa).

Furthermore, the time for which the coating is contacted with steam ispreferably at least 1 sec., and more preferably at least 3 sec., and itis preferably no greater than 100 sec., and more preferably no greaterthan 20 sec.

Sealing Treatment with Hot Water

With regard to the sealing treatment with hot water, for example, amethod in which an aluminum plate having an anodized coating formedthereon is immersed in hot water can be cited.

The hot water may contain an inorganic salt (e.g. a phosphate) or anorganic salt.

The temperature of the hot water is preferably at least 80° C., and morepreferably at least 95° C., and it is preferably no greater than 100° C.

Furthermore, the time for which immersion in hot water is carried out ispreferably at least 1 sec., and more preferably at least 3 sec., and itis preferably no greater than 100 sec., and more preferably no greaterthan 20 sec.

With regard to a hydrophilization treatment that is used in the presentinvention, there is an alkali metal silicate method, as disclosed inU.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734. In thismethod, a support is immersed in an aqueous solution of sodium silicate,etc., or subjected to electrolysis. In addition, there is a method inwhich a support is treated with potassium fluorozirconate, as describedin JP-B-36-22063, and a method in which a support is treated withpolyvinylphosphonic acid, as described in U.S. Pat. Nos. 3,276,868,4,153,461, and 4,689,272.

In the present invention, it is preferable for the support to have acenter line average roughness of 0.10 to 1.2 μm. It is preferable for itto be in this range since good adhesion to an image recording layer,good plate life, and good contamination resistance can be obtained.

(4-1-2) Step of Discharging Ink Composition onto Hydrophilic Support

When the ink composition or the inkjet recording ink composition of thepresent invention is discharged onto the surface of the above-mentionedhydrophilic support, the ink composition or the inkjet recording inkcomposition is preferably discharged after being heated to preferably40° C. to 80° C., and more preferably 25° C. to 30° C., so as to reducethe viscosity of the ink composition to preferably 7 to 30 mPa·s, andmore preferably 7 to 20 mPa·s. In particular, it is preferable to usethe ink composition having an ink viscosity at 25° C. of 35 to 500 mPa·ssince a large effect can be obtained. By employing this method, highdischarge stability can be realized. The radiation curing type inkcomposition such as the ink composition of the present inventiongenerally has a viscosity that is higher than that of a normal inkcomposition or a water-based ink used for an inkjet recording ink, andvariation in viscosity due to a change in temperature at the time ofdischarge is large. Viscosity variation in the ink has a large effect onchanges in liquid droplet size and changes in liquid droplet dischargespeed and, consequently, causes the image quality to be degraded. It istherefore necessary to maintain the ink discharge temperature asconstant as possible. In the present invention, the control range forthe temperature is desirably ±5° C. of a set temperature, preferably ±2°C. of the set temperature, and more preferably ±1° C. of the settemperature.

(4-1-3) Step of Curing Ink Composition by Irradiating Discharged InkComposition with Actinic Radiation so as to Form Hydrophobic Image onHydrophilic Support by Curing Ink Composition

The ink composition discharged onto the surface of the hydrophilicsupport is cured by irradiating with actinic radiation. This resultsfrom a sensitizing dye in a polymerization initiation system containedin the above-mentioned ink composition of the present inventionabsorbing actinic radiation, attaining an excited state, and coming intocontact with a polymerization initiator in the polymerization initiationsystem to thus decompose the polymerization initiator, and apolymerizable compound undergoing radical polymerization and beingcured.

The actinic radiation used in this process may include α rays, γ rays,an electron beam, X rays, UV rays, visible light, and IR rays. Althoughit depends on the absorption characteristics of the sensitizing dye, thepeak wavelength of the actinic radiation is, for example, 200 to 600 nm,preferably 300 to 450 nm, and more preferably 350 to 450 nm.Furthermore, in the present invention, the polymerization initiationsystem has sufficient sensitivity for low output actinic radiation. Theoutput of the actinic radiation as irradiation energy is therefore, forexample, 2,000 mJ/cm² or less, and is preferably 10 to 2,000 mJ/cm²,more preferably 20 to 1,000 mJ/cm², and yet more preferably 50 to 800mJ/cm². Moreover, the actinic radiation is applied so that theillumination intensity on the exposed surface is, for example, 10 to2,000 mW/cm², and preferably 20 to 1,000 mW/cm².

The ink composition of the present invention is desirably exposed tosuch actinic radiation for, for example, 0.01 to 120 sec., andpreferably 0.1 to 90 sec.

Irradiation conditions and a basic method for irradiation with actinicradiation are disclosed in JP-A-60-132767. Specifically, a light sourceis provided on either side of a head unit that includes an ink dischargedevice, and the head unit and the light source are made to scan by aso-called shuttle system. Irradiation with actinic radiation is carriedout after a certain time (e.g. 0.01 to 0.5 sec., preferably 0.01 to 0.3sec., and more preferably 0.01 to 0.15 sec.) has elapsed from when theink has landed. By controlling the time from ink landing to irradiationso as to be a minimum in this way, it becomes possible to prevent theink that has landed on a recording medium from spreading before beingcured. Furthermore, since the ink can be exposed before it reaches adeep area of a porous recording medium that the light source cannotreach, it is possible to prevent monomer from remaining unreacted, andas a result the odor can be reduced.

Furthermore, curing may be completed using another light source that isnot driven. WO99/54415 discloses, as an irradiation method, a methodemploying an optical fiber and a method in which a collimated lightsource is incident on a mirror surface provided on a head unit sideface, and a recorded area is irradiated with UV light.

By employing such a recording method, it is possible to maintain auniform dot diameter for landed ink even for various types of recordingmedia having different surface wettability, thereby improving the imagequality. In order to obtain a color image, it is preferable tosuperimpose colors in order from those with a low lightness. Bysuperimposing inks in order from one with low lightness, it is easy forradiation to reach a lower ink, the curing sensitivity is good, theamount of residual monomer decreases, odor is reduced, and animprovement in adhesion can be expected. Furthermore, although it ispossible to discharge all colors and then expose them at the same time,it is preferable to expose one color at a time from the viewpoint ofpromoting curing.

In this way, the above-mentioned ink composition of the presentinvention is cured by irradiation with actinic radiation to thus form ahydrophobic image on the surface of the hydrophilic support.

(4-2) Inkjet Recording Device

The inkjet recording device used in the present invention is notparticularly restricted, and a commercial inkjet recording device may beused. That is, in the present invention, recording on a recording mediummay be carried out using a commercial inkjet recording device.

The inkjet recording device that can be used in the present invention isequipped with, for example, an ink supply system, a temperature sensor,and an actinic radiation source.

The ink supply comprises, for example, a main tank containing the inkcomposition of the present invention, a supply pipe, an ink supply tankimmediately before an inkjet head, a filter, and a piezo system inkjethead. The piezo system inkjet head may be driven so as to discharge amultisize dot of 1 to 100 pL, and preferably 8 to 30 pL, at a resolutionof 320×320 to 4,000×4,000 dpi, preferably 400×400 to 1,600×1,600 dpi,and more preferably 720×720 dpi. Here, dpi referred to in the presentinvention means the number of dots per 2.54 cm.

As described above, since it is desirable for the radiation curing typeink to be discharged at a constant temperature, a section from the inksupply tank to the inkjet head is thermally insulated and heated. Amethod of controlling temperature is not particularly limited, but it ispreferable to provide, for example, temperature sensors at a pluralityof pipe section positions, and control heating according to the ink flowrate and the temperature of the surroundings. The temperature sensorsmay be provided on the ink supply tank and in the vicinity of the inkjethead nozzle. Furthermore, the head unit that is to be heated ispreferably thermally shielded or insulated so that the device main bodyis not influenced by the temperature of the outside air. In order toreduce the printer start-up time required for heating, or in order toreduce the thermal energy loss, it is preferable to thermally insulatethe head unit from other sections and also to reduce the heat capacityof the entire heated unit.

As an actinic radiation source, a mercury lamp, a gas/solid laser, etc.are mainly used, and for UV photocuring inkjet a mercury lamp and ametal halide lamp are widely known. However, from the viewpoint ofprotection of the environment, there has recently been a strong desirefor mercury not to be used, and replacement by a GaN semiconductor UVlight emitting device is very useful from industrial and environmentalviewpoints. Furthermore, LEDs (UV-LED) and LDs (UV-LD) have smalldimensions, long life, high efficiency, and low cost, and their use as aphotocuring inkjet light source can be expected.

Furthermore, light-emitting diodes (LED) and laser diodes (LD) may beused as the source of actinic radiation. In particular, when a UV raysource is needed, a UV-LED or a UV-LD may be used. For example, NichiaCorporation has marketed a violet LED having a wavelength of the mainemission spectrum of between 365 nm and 420 nm. Furthermore, when ashorter wavelength is needed, U.S. Pat. No. 6,084,250 discloses an LEDthat can emit actinic radiation whose wavelength is centered between 300nm and 370 nm. Furthermore, another violet LED is available, andirradiation can be carried out with radiation of a different UVbandwidth. The actinic radiation source particularly preferable in thepresent invention is a UV-LED, and a UV-LED having a peak wavelength at350 to 420 nm is particularly preferable.

The maximum illumination intensity of the LED on a recording medium ispreferably 10 to 2,000 mW/cm², more preferably 20 to 1,000 mW/cm², andparticularly preferably 50 to 800 mJ/cm².

In accordance with the present invention, it is possible to provide anink composition that cures with high sensitivity when exposed toradiation, can form a high quality image, has excellent adhesion to arecording medium, and has low odor, and an inkjet recording methodemploying the ink composition.

Furthermore, a printed material obtained using the ink compositionhaving low odor and capable of curing with high sensitivity when exposedto ultraviolet rays has high image quality and excellent strength for animage area. Similarly, in accordance with use of the ink composition ofthe present invention, there is exhibited the effect that a lithographicprinting plate having low odor and high image quality can be producedbased on digital data.

EXAMPLES

The present invention is explained in further detail by reference toExamples and Comparative Examples. However, the present invention shouldnot be construed as being limited to these Examples.

IRGACURE 184, IRGACURE 819, IRGACURE 250, IRGACURE 907, and Darocur ITX(polymerization initiator) used in the present invention are commercialproducts manufactured by Ciba Specialty Chemicals (CSC).

Example 1

Preparation of Pigment Dispersions

Yellow, magenta, cyan, and black pigment dispersions 1 were prepared inaccordance with the method described below. Dispersion conditions wereappropriately adjusted using a known dispersing machine so that theaverage particle size of pigment particles was in the range of 0.2 to0.3 μm, and they were subsequently filtered using a filter whileheating. Yellow pigment dispersion 1 Cl Pigment Yellow 13 20 parts byweight Polymeric dispersant (Solsperse series manufactured by Avecia) 20parts by weight Diethylene glycol divinyl ether (manufactured by BASF)60 parts by weight Magenta pigment dispersion 1 Cl Pigment Red 57:1 20parts by weight Polymeric dispersant (Solsperse series manufactured byAvecia) 20 parts by weight Diethylene glycol divinyl ether (manufacturedby BASF) 60 parts by weight Cvan pigment dispersion 1 Cl Pigment Blue15:3 20 parts by weight Polymeric dispersant (Solsperse seriesmanufactured by Avecia) 20 parts by weight Diethylene glycol divinylether (manufactured by BASF) 60 parts by weight Black pigment dispersion1 Cl Pigment black 7 20 parts by weight Polymeric dispersant (Solsperseseries manufactured by Avecia) 20 parts by weight Diethylene glycoldivinyl ether (manufactured by BASF) 60 parts by weight Preparation ofinks The components below were mixed and filtered using a filter to giveinks 1 of each color. Yellow ink 1 The above yellow pigment dispersion 15 parts by weight Polymerizable compound A: dipropylene glycoldiacrylate 60 parts by weight (difunctional monomer, manufactured byDaicel-UCB Co., Ltd.) Polymerizable compound B: ODA (monofunctionalmonomer, manufactured by 20 parts by weight Daicel Chemical)Polymerization initiator 1 (IRGACURE 184, manufactured by CSC) 5 partsby weight Polymerization initiator 2 (IRGACURE 819, manufactured by CSC)5 parts by weight Polymerization inhibitor: benzoquinone 0.3 parts byweight Fragrance A (Valencia orange oil) 0.2 parts by weight Fragrance B(cis-3-cyclohexyl acetate) 0.1 parts by weight

Magenta ink 1 The above magenta pigment dispersion 1 5 parts by weightPolymerizable compound A: dipropylene glycol diacrylate 60 parts byweight Polymerizable compound B: ODA 20 parts by weight Polymerizationinitiator 1 (IRGACURE 184, manufactured by CSC) 5 parts by weightPolymerization initiator 2 (IRGACURE 819, manufactured by CSC) 5 partsby weight Polymerization inhibitor: benzoquinone 0.3 parts by weightFragrance A (Valencia orange oil) 0.2 parts by weight Fragrance B(cis-3-cyclohexyl acetate) 0.1 parts by weight Cvan ink 1 The above cyanpigment dispersion 1 5 parts by weight Polymerizable compound A:dipropylene glycol diacrylate 60 parts by weight Polymerizable compoundB: ODA 20 parts by weight Polymerization initiator 1 (IRGACURE 184,manufactured by CSC) 5 parts by weight Polymerization initiator 2(IRGACURE 819, manufactured by CSC) 5 parts by weight Polymerizationinhibitor: benzoquinone 0.3 parts by weight Fragrance A (Valencia orangeoil) 0.2 parts by weight Fragrance B (cis-3-cyclohexyl acetate) 0.1parts by weight Black ink 1 The above black pigment dispersion 1 5 partsby weight Polymerizable compound A: dipropylene glycol diacrylate 60parts by weight Polymerizable compound B: ODA 20 parts by weightPolymerization initiator 1 (IRGACURE 184, manufactured by CSC) 5 partsby weight Polymerization initiator 2 (IRGACURE 819, manufactured by CSC)5 parts by weight Polymerization inhibitor: benzoquinone 0.3 parts byweight Fragrance A (Valencia orange oil) 0.2 parts by weight Fragrance B(cis-3-cyclohexyl acetate) 0.1 parts by weightInkjet Image Recording

Subsequently, recording was carried out on a recording medium using acommercial inkjet recording device having a piezo system inkjet nozzle.The ink supply system comprised a main tank, a supply pipe, an inksupply tank immediately before an inkjet head, a filter, and a piezosystem inkjet head, and a section from the ink supply tank to the inkjethead was thermally insulated and heated. Temperature sensors wereprovided on the ink supply tank and in the vicinity of the nozzle of theinkjet head, and the temperature was controlled so that the nozzlesection was always at 70° C.±2° C. The piezo system inkjet head wasdriven so as to discharge a multisize dot of 8 to 30 pL at a resolutionof 720×720 dpi. The exposure system, the main scanning speed, and thedischarge frequency were adjusted so that, after landing, UV light wasfocused to give an exposure area illumination intensity of 100 mW/cm²,and irradiation started 0.1 sec. after the ink landed on the recordingmedium. Furthermore, the exposure time was made variable, and exposureenergy was applied. Here, dpi referred to in the present inventiondenotes the number of dots per 2.54 cm.

The inks of each color prepared above were discharged in the orderblack, cyan, magenta, and yellow at an environmental temperature of 25°C., and each color was irradiated with UV rays using a VZero 085 metalhalide lamp manufactured by Integration Technology. As an energy levelthat could completely cure the inks so that tackiness disappeared whentouched by hand, the total exposure energy per color was 300 mJ/cm² forall the colors. As recording media, a grained aluminum support, atransparent biaxially stretched polypropylene film whose surface hadbeen treated so as to impart printability, a soft vinyl chloride sheet,a cast coat paper, and a commercial recycled paper were used, each colorimage was recorded, and an image having high resolution without dotspreading was obtained in all cases. Furthermore, for high qualitypaper, the ink did not penetrate to the reverse side, the ink wassufficiently cured, and there was hardly any odor due to unreactedmonomer. Moreover, the ink recorded on the film had sufficientflexibility, the ink did not crack when bent, and there was no problemin an adhesion test involving peeling with cellophane tape.

Examples 2 to 10

Preparation of Inks

Magenta Inks 2 to 10 were prepared in accordance with the methoddescribed below.

Magenta Inks 2 to 5

Magenta inks 2 to 5 were prepared in the same manner as for the abovemagenta ink 1 except that Fragrance A and Fragrance B were changed tothe fragrances below. TABLE 2 Magenta ink Fragrance A Fragrance BMagenta ink 2 Bergamot oil cis-3-hexanol Magenta ink 3 d-LimoneneMethyloctine carbonate Magenta ink 4 Petitgrain oil CuminaldehydeMagenta ink 5 Neroli oil Ethyl benzoate

Magenta ink 6 was prepared by mixing the components below, followed byfiltering using a filter.

Magenta Ink 6 The above magenta pigment dispersion 1 5 parts by weightPolymerizable compound C: Celloxide 2021 35 parts by weight (epoxycompound: manufactured by Daicel-UCB Co., Ltd.) Polymerizable compoundD: OXT-221 55 parts by weight (oxetane compound: manufactured byToagosei Co., Ltd.) Polymerization initiator 3 (IRGACURE 250, 5 parts bymanufactured by CSC) weight Polymerization initiator 4 (Darocur ITX, 5parts by manufactured by CSC) weight Polymerization inhibitor:diethylaniline 0.2 parts by weight Fragrance C (ethyl isovalerate) 0.2parts by weight Fragrance D (ethylvanillin) 0.1 parts by weight

Magenta Inks 7 to 10

Magenta inks 7 to 10 were prepared in the same manner as for the abovemagenta ink 6 except that Fragrance C and Fragrance D of Magenta ink 6were changed to the fragrances below. TABLE 3 Magenta ink Fragrance CFragrance D Magenta ink 7 Geranyl acetate Vanillin Magenta ink 8 Methylcinnamate Camphor Magenta ink 9 Linalyl acetate Ionone Magenta ink 10Acetyl cedrene Rose oxideMagenta Ink 11:

Comparative Example 1

Magenta ink 11 was prepared in the same manner as for magenta ink 1except that the fragrances of magenta ink 1 were not used.

Magenta Ink 12:

Comparative Example 2

Magenta ink 12 was prepared in exactly the same manner as for magentaink 6 except that Fragrance C and Fragrance D were not used.

Example 11

Magenta ink 13 was prepared in the same manner as for Magenta ink 1except that Compound M-1 below (oxidation potential +1.40 V) was used asan oil-soluble dye instead of CI Pigment Red 57:1 and filtration wascarried out using a filter having an absolution filtration accuracy of 2μm.

Example 12

Magenta ink 14 was prepared in the same manner as for Magenta ink 1except that Compound M-2 below (oxidation potential +0.70 V) was used asan oil-soluble dye instead of CI Pigment Red 57:1 and filtration wascarried out using a filter having an absolution filtration accuracy of 2μm.

Inkjet Image Recording

Magenta images were formed in the same manner as in the method describedin Example 1 using Magenta inks 2 to 14 prepared above and Magenta ink 1prepared in Example 1.

Evaluation of Inkjet Image

The images thus formed were subjected to evaluation in accordance withthe methods described below in terms of sensitivity required for curing,penetration into commercial recycled paper, ink spreading on a grainedaluminum support, adhesion, plate life, and storage stability. Theresults are given in Table 4.

Curing Sensitivity Measurement

The exposure energy intensity (mJ/cm²) when a feeling of tackinessdisappeared on the image surface after irradiation with ultraviolet rayswas defined as the curing sensitivity. The smaller the value, the higherthe sensitivity.

Evaluation of Penetration into Commercial Recycled Paper

Images printed on commercial recycled paper were evaluated in terms ofpenetration in accordance with the criteria below.

Good: Hardly any penetration, no odor of residual monomer.

Fair: Slight penetration, slight odor of residual monomer.

Poor: Ink obviously penetrated to the reverse side, and strong odor ofresidual monomer.

Evaluation of Ink Spread on Grained Aluminum Support

With respect to an image printed on a grained aluminum support, inkspread was evaluated in accordance with the criteria below.

Good: no spread between adjacent dots.

Fair: dots slightly spread.

Poor: dots spread and image was obviously blurred.

Evaluation of Adhesion to Grained Aluminum Support

With regard to the printed images formed above, a completely undamagedsample and a sample whose printed surface was crosshatched with 11 cutsin both lengthwise and widthwise directions at intervals of 1 mm inaccordance with JIS K 5400 to give 100 1 mm squares were prepared,cellophane tape was affixed to the surface of each sample and peeled offquickly at an angle of 90 degrees, and the condition of the remainingprinted image that had not been peeled off was evaluated in accordancewith the criteria below.

Good: printed image was not peeled off at all in the crosshatch test.

Fair: the ink was slightly peeled off in the crosshatch test, but unlessthe ink surface was damaged little was peeled off.

Poor: easily peeled off by cellophane tape under both conditions.

Evaluation of Plate Life

An image printed on a grained aluminum support prepared above was usedas a printing plate, printing was carried out using a Heidel KOR-Dmachine, and a relative comparison of the number of prints completed wasused as an index for the plate life (the number obtained for Example 1was defined as 100). The larger the number, the longer the plate life,which is preferable.

Storage Stability Evaluation

After storing the prepared ink at 75% RH and 60° C. for 3 days, the inkviscosity at the discharge temperature was measured, and an increase inthe ink viscosity was expressed as a viscosity ratio (afterstorage/before storage). When the viscosity was unchanged and the ratiowas close to 1.0, the storage stability was good, and if the ratioexceeded 1.5, clogging might undesirably be caused during discharge.

Evaluation of Odor (Masking Level)

Evaluation was carried out by eight specialist panelists in accordancewith the criteria below.

Evaluation Criteria (Evaluation Points):

5 (points): eight among eight recognized a masking effect.

4 (points): 6 to 7 people among eight recognized a masking effect.

3 (points): 4 to 5 people among eight recognized a masking effect.

2 (points): 1 to 3 people among eight recognized a masking effect.

1 (points): masking effect could not be recognized.

When the number of masking points is equal to or greater than 4, therecan be expected to be no problem in practical use.

The evaluation results are given in Table 4. TABLE 4 Curing Magentasensitivity Ink Plate Storage Masking Example ink (mJ/cm²) Penetrationspreading Adhesion life stability level Example 1 1 300 Good Good Good100 1.1 5 Example 2 2 310 Good Good Good 110 1.1 5 Example 3 3 300 GoodGood Good 120 1.1 4 Example 4 4 290 Good Good Good 110 1.2 5 Example 5 5280 Good Good Good 130 1.2 4 Example 6 6 120 Good Good Good 130 1.2 5Example 7 7 110 Good Good Good 140 1.2 4 Example 8 8 100 Good Good Good150 1.3 5 Example 9 9 110 Good Good Good 140 1.2 5 Example 10 10 120Good Good Good 130 1.2 4 Example 11 13 100 Good Good Good 150 1.2 4Example 12 14 180 Good Good Good 140 1.3 4 Comp. Ex. 1 11 320 Good FairGood 90 1.4 1 Comp. Ex. 2 12 140 Fair Good Fair 100 1.5 1

Example 13

A magenta image was formed using Magenta ink 6 by the same method as inExample 1 except that a UV light-emitting diode (UV-LED) was usedinstead of the VZero 085 metal halide lamp manufactured by IntegrationTechnology.

In this embodiment, an NCCU033 manufactured by Nichia Corporation wasused as the UV-LED. The LED emits UV light at a wavelength of 365 nmfrom 1 chip, and by applying a current of about 500 mA, light of about100 mW is emitted from the chip. A plurality thereof were aligned atintervals of 7 mm to give a power of 0.3 W/cm² on the surface of arecording medium (hereinafter, also called a medium). The time fromlanding to irradiation and the exposure time can be varied by thetransport speed of the medium and the distance between a head and theLED in the transport direction. In this embodiment, irradiation wascarried out about 0.5 sec. after landing.

The exposure energy on the medium was adjustable in the range of 0.01 to15 J/cm² by setting the distance from the medium and the transportspeed.

It was found that the energy level that could completely cure the inksso that tackiness disappeared when touched by hand was 250 mJ/cm². Asrecording media, a grained aluminum support, a transparent biaxiallystretched polypropylene film whose surface had been treated so as toimpart printability, a soft vinyl chloride sheet, a cast coat paper, anda commercial recycled paper were used, color images were recorded, andan image having high resolution without dot spreading was obtained inall cases. Furthermore, for high quality paper, the ink did notpenetrate to the reverse side, the ink was sufficiently cured, and therewas hardly any odor due to unreacted monomer. Moreover, the ink recordedon the film had sufficient flexibility, the ink did not crack when bent,and there was no problem in an adhesion test involving peeling withSellotape (registered trademark).

From the results above, the ink composition employing the fragrance ofthe present invention had high sensitivity when exposed to radiation,formed a high quality image in terms of image formation properties onpaper, and had good storage stability and, furthermore, when it was usedfor formation of a printing plate, the plate life was good, a highquality image could be formed, and the odor was low.

1. An ink composition comprising: a) a polymerizable compound; b) apolymerization initiator; c) a coloring agent; and d) a fragrance. 2.The ink composition according to claim 1, wherein the fragrance d)comprises a natural fragrance.
 3. The ink composition according to claim1, wherein the fragrance d) comprises a synthetic fragrance.
 4. The inkcomposition according to claim 1, wherein the fragrance d) comprises anester compound.
 5. The ink composition according to claim 1, wherein thefragrance d) comprises a terpene compound.
 6. The ink compositionaccording to claim 1, wherein the polymerizable compound a) iscationically polymerizable, and the polymerization initiator b) is aphoto-acid generator.
 7. The ink composition according to claim 1,wherein the coloring agent c) is a pigment or an oil-soluble dye.
 8. Theink composition according to claim 7, wherein the oil-soluble dye has anoxidation potential of at least 1.0 V (vs SCE).
 9. The ink compositionaccording to claim 1, wherein it is for inkjet recording.
 10. An inkjetrecording method comprising: (a) a step of discharging an inkcomposition onto a recording medium; and (b) a step of curing the inkcomposition by irradiating the discharged ink composition with actinicradiation, the ink composition being the ink composition according toclaim
 1. 11. The inkjet recording method according to claim 10, whereinthe actinic radiation is UV radiation having a peak light emissionwavelength in the range of 350 to 420 nm and is emitted by alight-emitting diode for emitting UV radiation whose maximumillumination intensity on the surface of a recording medium is 10 to2,000 mW/cm².
 12. A printed material recorded by the inkjet recordingmethod according to claim
 10. 13. A process for producing a lithographicprinting plate, the process comprising: (a) a step of discharging theink composition according to claim 1 onto a hydrophilic support; and (b)a step of curing the ink composition by irradiating the discharged inkcomposition with actinic radiation so as to form a hydrophobic image onthe hydrophilic support by curing the ink composition.
 14. Alithographic printing plate produced by the lithographic printing plateproduction process according to claim 13.